U.S. patent application number 17/281197 was filed with the patent office on 2022-04-07 for method and device for estimating inter-terminal path loss in wireless communication system.
The applicant listed for this patent is Samsung Electronics Co., Ltd.. Invention is credited to Juho LEE, Jinyoung OH, Sungjin PARK, Hyunseok RYU, Jeongho YEO.
Application Number | 20220110067 17/281197 |
Document ID | / |
Family ID | |
Filed Date | 2022-04-07 |
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United States Patent
Application |
20220110067 |
Kind Code |
A1 |
RYU; Hyunseok ; et
al. |
April 7, 2022 |
METHOD AND DEVICE FOR ESTIMATING INTER-TERMINAL PATH LOSS IN
WIRELESS COMMUNICATION SYSTEM
Abstract
The present disclosure relates to a method and apparatus for
estimating inter-terminal sidelink path loss for control
information and data information transmission between terminals. A
path loss estimation method of a transmission terminal in a
wireless communication system according to an embodiment may
include transmitting a signal for path loss estimation to a
reception terminal, receiving a path loss estimation result report
from the reception terminal in response to the signal for path loss
estimation, configuring a transmission power based on the path loss
estimation result report, and performing a sidelink transmission
with the reception terminal with the configured transmission
power.
Inventors: |
RYU; Hyunseok; (Suwon-si,
KR) ; YEO; Jeongho; (Suwon-si, KR) ; OH;
Jinyoung; (Suwon-si, KR) ; PARK; Sungjin;
(Suwon-si, KR) ; LEE; Juho; (Suwon-si,
KR) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Samsung Electronics Co., Ltd. |
Suwon-si |
|
KR |
|
|
Appl. No.: |
17/281197 |
Filed: |
September 20, 2019 |
PCT Filed: |
September 20, 2019 |
PCT NO: |
PCT/KR2019/012244 |
371 Date: |
November 15, 2021 |
International
Class: |
H04W 52/24 20060101
H04W052/24; H04W 52/38 20060101 H04W052/38; H04W 56/00 20060101
H04W056/00; H04L 5/00 20060101 H04L005/00 |
Foreign Application Data
Date |
Code |
Application Number |
Sep 27, 2018 |
KR |
10-2018-0115354 |
Jun 28, 2019 |
KR |
10-2019-0078301 |
Claims
1.-15. (canceled)
16. A path loss estimation method of a transmission terminal in a
wireless communication system, the path loss estimation method
comprising: transmitting a signal for path loss estimation to a
reception terminal; receiving a report for path loss estimation
from the reception terminal, based on the signal for path loss
estimation; determining a transmission power based on the report
for path loss estimation; and performing a sidelink transmission
with the reception terminal based on the determined transmission
power.
17. The path loss estimation method of claim 16, wherein the
receiving of the report for path loss estimation from the reception
terminal based on the signal for path loss estimation comprises
receiving a layer 3 RSRP (L3-RSRP) measured by the reception
terminal through a radio resource control (RRC) message transmitted
via a sidelink data channel (PSSCH).
18. The path loss estimation method of claim 16, wherein the signal
for path loss estimation comprises a demodulation reference signal
(DMRS) transmitted via a sidelink data channel (physical sidelink
shared channel (PSSCH)).
19. The path loss estimation method of claim 16, wherein the signal
for path loss estimation is transmitted in case that the
transmission terminal determines that the transmission of the
signal for path loss estimation is necessary.
20. The path loss estimation method of claim 16, wherein the report
for path loss estimation from the reception terminal is received
periodically.
21. The path loss estimation method of claim 16, wherein the report
for path loss estimation from the reception terminal is received in
case that an RSRP value measured by the reception terminal is equal
to or greater than a threshold value.
22. The path loss estimation method of claim 16, wherein the report
for path loss estimation from the reception terminal is received in
case that an RSRP value measured by the reception terminal is equal
to or less than a threshold value.
23. The path loss estimation method of claim 1, further comprising:
transmitting a configuration for a measurement for path loss
estimation via PC-5 RRC signaling to the reception terminal.
24. A path loss estimation method of a reception terminal in a
wireless communication system, the path loss estimation method
comprising: receiving a signal for path loss estimation from a
transmission terminal; measuring reference signal received power
(RSRP) based on the signal for path loss estimation; and
transmitting a report for path loss estimation comprising the RSRP
to the transmission terminal.
25. The path loss estimation method of claim 24, wherein the
transmitting of the report for path loss estimation comprising the
RSRP to the transmission terminal comprises transmitting a layer 3
RSRP (L3-RSRP) through a radio resource control (RRC) message
transmitted via a sidelink data channel (PSSCH).
26. The path loss estimation method of claim 24, wherein the signal
for path loss estimation comprises a demodulation reference signal
(DMRS) transmitted via a sidelink data channel (physical sidelink
shared channel (PSSCH)).
27. The path loss estimation method of claim 24, wherein the report
for path loss estimation from the reception terminal is received
periodically.
28. The path loss estimation method of claim 24, further
comprising: receiving a configuration for a measurement for path
loss estimation via PC-5 RRC signaling from the transmission
terminal.
29. A transmission terminal comprising: a transceiver; a memory
storing a path loss estimation method program and data of the
transmission terminal; and a processor configured to execute the
program stored in the memory to transmit a signal for path loss
estimation to a reception terminal, receive a report for path loss
estimation from the reception terminal based on the signal for path
loss estimation, determine transmission power based on the report
for path loss estimation, and perform sidelink transmission with
the reception terminal based on the determined transmission
power.
30. A reception terminal comprising: a transceiver; a memory
storing a path loss estimation method program and data of the
reception terminal; and a processor configured to execute the
program stored in the memory to receive a signal for path loss
estimation from a transmission terminal, measure reference signal
received power (RSRP) based on the signal for path loss estimation,
and transmit a report for path loss estimation comprising the RSRP
to the transmission terminal.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a 371 of International Application No.
PCT/KR2019/012244 filed on Sep. 20, 2019, which claims priority to
Korean Patent Application No. 10-2018-0115354 filed on Sep. 27,
2018 and Korean Patent Application No. 10-2019-0078301 filed on
Jun. 28, 2019, the disclosures of which are herein incorporated by
reference in their entirety.
BACKGROUND
1. Field
[0002] The present disclosure relates to a method and apparatus for
estimating inter-terminal sidelink path loss for transmission of
control information and data information between terminals, and
more particularly, to a method and apparatus for estimating path
loss by using a signal for path loss estimation transmitted via a
sidelink and controlling transmission power of the sidelink.
2. Description of Related Art
[0003] In order to meet the increasing demand with respect to
wireless data traffic after the commercialization of 4.sup.th
generation (4G) communication systems, efforts have been made to
develop enhanced 5.sup.th generation (5G) communication systems or
pre-5G communication systems. For this reason, 5G communication
systems or pre-5G communication systems are called `beyond 4G
network communication systems` or `post long term evolution (LTE)
systems`. 5G communication systems defined by the 3.sup.rd
generation partnership project (3GPP) are called new radio (NR)
systems. In order to achieve a high data rate, consideration is
given to implementing 5G communication systems in ultra-high
frequency bands (millimeter wave (mmW)) (e.g., 60 GHz). In order to
reduce the path loss of radio waves and increase a transmission
distance of radio waves in ultra-high frequency bands, for 5G
communication systems, technologies such as beamforming, massive
multiple-input multiple-output (MIMO), full dimensional MIMO
(FD-MIMO), array antenna, analog beamforming, and large scale
antenna have been discussed, and have been applied to NR systems.
Also, in order to improve system networks, for 5G communication
systems, technologies such as evolved small cell, advanced small
cell, cloud radio access network (cloud RAN), ultra-dense network,
device-to-device (D2D) communication, wireless backhaul, moving
network, cooperative communication, coordinated multi-points
(CoMP), and interference cancellation have been developed.
Furthermore, for 5G communication systems, advanced coding
modulation (ACM) schemes such as hybrid frequency-shift keying
(FSK) and quadrature amplitude modulation (QAM) modulation (FQAM)
and sliding window superposition coding (SWSC) and enhanced network
access schemes such as filter-bank multi-carrier (FBMC),
non-orthogonal multiple access (NOMA), and sparse code multiple
access (SCMA) have been developed.
[0004] The Internet is evolving from a human-centered connection
network through which humans create and consume information to an
Internet of Things (IoT) network through which distributed elements
such as objects exchange and process information. Internet of
Everything (IoE) technology, which is a combination of IoT
technology and big data processing technology through connection
with a cloud server, is also emerging. In order to implement the
IoT, technology elements such as sensing technology, wired/wireless
communication and network infrastructure, service interface
technology, and security technology are required, and thus
technology for inter-object connection, such as sensor network,
machine to machine (M2M) communication, or machine-type
communication (MTC), has recently been studied. In an IoT
environment, intelligent Internet technology (IT) services that
collect and analyze data generated by connected objects and create
new value in human life may be provided. The IoT may be applied to
fields such as smart homes, smart buildings, smart cities, smart
cars or connected cars, smart grids, health care, smart home
appliances, and advanced medical services through convergence and
integration of existing information technology (IT) and various
industries.
[0005] Accordingly, various attempts have been made to apply 5G
communication systems to IoT networks. For example, technologies
such as sensor network, M2M communication, and MTC are implemented
by 5G communication technologies such as beamforming, MIMO, and
array antenna. The application of a cloud RAN as big data
processing technology may also be considered as an example of
convergence between 5G technology and IoT technology.
[0006] In vehicle communication, standardization of
vehicle-to-everything (V2X) based on LTE systems in 3GPP Rel-14 and
Rel-15 has been completed, based on a device-to-device (D2D)
communication structure. Currently, attempts have been made to
develop V2X based on 5G NR systems. V2X based on 5G or NR systems
may support unicast communication, groupcast (or multicast)
communication, broadcast communication, etc., between terminals.
Also, unlike V2X based on LTE systems, which aims at transmitting
and receiving basic safety information required for on-road driving
of vehicles, V2X based on 5G or NR systems aims at providing more
advanced services such as platooning, advanced driving, extended
sensor, and remote driving. Such various services and scenarios
require higher reliability and a higher data rate than in LTE
system-based D2D or LTE system-based V2X. Accordingly, V2X based on
5G or NR systems needs to support link adaptation based on
measurement of the quality of a sidelink between terminals.
[0007] Disclosed embodiments provide a method and apparatus for
estimating inter-terminal sidelink path loss, to support high
reliability and a high data rate.
[0008] Also, disclosed embodiments provide a method and apparatus
for controlling inter-terminal sidelink transmission power
according to path loss estimation.
[0009] Furthermore, disclosed embodiments provide a method and
apparatus for effectively providing a service in a mobile
communication system.
SUMMARY
[0010] A path loss estimation method of a transmission terminal in
a mobile communication system according to an embodiment may
include transmitting a signal for path loss estimation to a
reception terminal, receiving a path loss estimation result report
from the reception terminal in response to the signal for path loss
estimation, configuring a transmission power based on the path loss
estimation result report, and performing a sidelink transmission
with the reception terminal with the configured transmission
power.
[0011] A path loss estimation method of a reception terminal in a
wireless communication system according to an embodiment may
include receiving a signal for path loss estimation from a
transmission terminal, measuring reference signal received power
(RSRP) based on the signal for path loss estimation, and
transmitting a path loss estimation result report including the
RSRP to the transmission terminal.
[0012] A transmission terminal according to an embodiment may
include a transceiver, a memory storing a path loss estimation
method program and data of the transmission terminal, and a
processor configured to execute the program stored in the memory to
transmit a signal for path loss estimation to a reception terminal,
receive a path loss estimation result report from the reception
terminal in response to the signal for path loss estimation,
configure transmission power based on the path loss estimation
result report, and perform sidelink transmission with the reception
terminal with the configured transmission power.
[0013] A reception terminal according to an embodiment may include
a transceiver, a memory storing a path loss estimation method
program and data of the reception terminal, and a processor
configured to execute the program stored in the memory to receive a
signal for path loss estimation from a transmission terminal,
measure reference signal received power (RSRP) based on the signal
for path loss estimation, and transmit a path loss estimation
result report including the RSRP to the transmission terminal.
[0014] According to an embodiment, transmission parameters of
sidelink control information and data information may be adjusted
according to channel quality of a sidelink. Accordingly, the
reliability and a data rate of the sidelink control information and
the data information in a vehicle communication system, a D2D
system, etc. may be improved. Also, the amount of interference
caused by a nearby cell or vehicle may be reduced. Accordingly,
more efficient communication between terminals may be supported.
Furthermore, a service may be effectively provided in a mobile
communication system.
BRIEF DESCRIPTION OF THE DRAWINGS
[0015] FIG. 1 is a view for describing a vehicle-to-everything
(V2X) system to which a disclosed embodiment is applied.
[0016] FIG. 2 is a view for describing a V2X communication method
performed through a sidelink.
[0017] FIG. 3 is a diagram for describing a method by which a user
equipment (UE) estimates downlink path loss (PL) in an existing
cellular system.
[0018] FIG. 4 is a diagram for describing a method of estimating
inter-UE sidelink path loss, according to a disclosed
embodiment.
[0019] FIG. 5 is a diagram for describing a method of estimating
inter-UE sidelink path loss, according to another disclosed
embodiment.
[0020] FIG. 6 is a diagram for describing a method of transmitting
and receiving a path loss measurement signal to estimate sidelink
path loss, according to a disclosed embodiment.
[0021] FIG. 7 is a diagram for describing a method of transmitting
and receiving a path loss measurement signal to estimate sidelink
path loss, according to another disclosed embodiment.
[0022] FIG. 8A is a diagram for describing a method of transmitting
and receiving a path loss measurement signal to estimate inter-UE
sidelink path loss, according to another disclosed embodiment.
[0023] FIG. 8B is a diagram for describing in more detail a method
of estimating inter-UE sidelink path loss according to an
embodiment of FIG. 8A.
[0024] FIG. 8C is another diagram describing in more detail a
method of estimating inter-UE sidelink path loss according to an
embodiment of FIG. 8A.
[0025] FIG. 8D is a diagram for describing a medium access control
control element (MAC CE) format for reporting an inter-UE sidelink
reference signal received power (RSRP) value, according to a
disclosed embodiment.
[0026] FIG. 9 is a diagram for describing a method of transmitting
and receiving a path loss measurement signal to estimate inter-UE
sidelink path loss, according to another disclosed embodiment.
[0027] FIG. 10 is a diagram for describing a method of transmitting
and receiving a path loss measurement signal to estimate inter-UE
sidelink path loss, according to another disclosed embodiment.
[0028] FIG. 11 is a flowchart illustrating a path loss estimation
operation of a transmission UE, according to a disclosed
embodiment.
[0029] FIG. 12 is a flowchart illustrating a path loss estimation
operation of a reception UE, according to a disclosed
embodiment.
[0030] FIG. 13 is a flowchart illustrating a path loss estimation
operation of a transmission UE, according to another disclosed
embodiment.
[0031] FIG. 14 is a flowchart illustrating a path loss estimation
operation of a reception UE, according to another disclosed
embodiment.
[0032] FIG. 15 is a block diagram illustrating a structure of a
transmission UE, according to an embodiment.
[0033] FIG. 16 is a block diagram illustrating a structure of a
reception UE, according to an embodiment.
DETAILED DESCRIPTION
[0034] A path loss estimation method of a transmission terminal in
a mobile communication system according to an embodiment may
include transmitting a signal for path loss estimation to a
reception terminal, receiving a path loss estimation result report
from the reception terminal in response to the signal for path loss
estimation, configuring transmission power based on the path loss
estimation result report, and performing sidelink transmission with
the reception terminal with the configured transmission power.
[0035] In an embodiment, the path loss estimation result report may
include at least one layer 1 reference signal received power
(L1-RSRP) measured by the reception terminal, wherein the receiving
of the path loss estimation result report from the reception
terminal in response to the signal for path loss estimation
includes receiving the at least one L1-RSRP measured by the
reception terminal via a sidelink feedback channel (physical
sidelink feedback channel (PSFCH)) or a medium access control
control element (MAC CE) transmitted via a sidelink data channel
(physical sidelink shared channel (PSSCH)).
[0036] In an embodiment, the MAC CE may include the at least one
L1-RSRP, wherein, when the MAC CE includes a plurality of L1-RSRPs,
the MAC CE includes a user equipment (UE) ID.
[0037] In an embodiment, the path loss estimation result report may
include layer 3 RSRP (L3-RSRP) measured by the reception terminal,
wherein the receiving of the path loss estimation result report
from the reception terminal in response to the signal for path loss
estimation includes receiving the L3-RSRP measured by the reception
terminal through a radio resource control (RRC) message transmitted
via a sidelink data channel (PSSCH).
[0038] In an embodiment, the receiving of the path loss estimation
result report from the reception terminal in response to the signal
for path loss estimation may include receiving the path loss
estimation result report after the signal for path loss estimation
is transmitted to the reception terminal, before a pre-configured
timer expires, or during a pre-configured second time before,
after, or before and after a point of time when a pre-configured
first time has elapsed or a point of time when a pre-configured
number of slots are received.
[0039] In an embodiment, when the path loss estimation result
report is not received before the pre-configured timer expires, the
path loss estimation method may further include transmitting, to
the reception terminal, information indicating that the path loss
estimation result report has not been received.
[0040] In an embodiment, the signal for path loss estimation may
include at least one signal from among a sidelink synchronization
signal including at least one of a primary sidelink synchronization
signal (PSSS) and a secondary sidelink synchronization signal
(SSSS), a demodulation reference signal (DMRS) transmitted via at
least one of a sidelink broadcast channel (physical sidelink
broadcast channel (PSBCH)), a sidelink control channel (physical
sidelink control channel (PSCCH)), and a sidelink data channel
(physical sidelink shared channel (PSSCH)), and a reference signal
for supporting a sidelink operation.
[0041] In an embodiment, the transmitting of the signal for path
loss estimation to the reception terminal may include transmitting
the signal for path loss estimation to the reception terminal, in
at least one case from among a case where a command for
transmission of the signal for path loss estimation is received
from a base station, a case where reference signal received power
(RSRP) measured by the transmission terminal for a signal for
downlink path loss estimation transmitted by the base station is
equal to or greater than a configured threshold value or equal to
or less than a configured threshold value, a case where the
transmission terminal determines that the signal for path loss
estimation needs to be transmitted, and a case where a transmission
request signal of the signal for path loss estimation is received
from the reception terminal.
[0042] In an embodiment, the transmitting of the signal for path
loss estimation to the reception terminal may include configuring,
as transmission power of the signal for path loss estimation, at
least one from among pre-configured transmission power, maximum
transmission power of the transmission terminal, transmission power
according to configuration of the base station, transmission power
determined based on RSRP measured by the transmission terminal for
a signal for downlink path loss estimation transmitted by the base
station, and transmission power determined based on RSRP measured
by the transmission terminal for a transmission request signal of
the signal for path loss estimation received from the reception
terminal.
[0043] In an embodiment, the receiving of the path loss estimation
result report from the reception terminal in response to the signal
for path loss estimation may include receiving the path loss
estimation result report periodically or aperiodically according to
at least one of configuration of a base station and sidelink
control information.
[0044] In an embodiment, the path loss estimation method may
further include transmitting, to the reception terminal,
information on the transmission power of the signal for path loss
estimation including at least one of offset information between a
configured reference signal and a transmission power value of the
signal for path loss estimation and the transmission power value of
the signal for path loss estimation.
[0045] In an embodiment, the signal for path loss estimation and
the information on the transmission power of the signal for path
loss estimation may be transmitted via the same channel or
different channels.
[0046] In an embodiment, the performing of the sidelink
transmission with the reception terminal with the configured
transmission power may include transmitting at least one of
sidelink control information and sidelink data to the reception
terminal.
[0047] A path loss estimation method of a reception terminal in a
wireless communication system according to an embodiment may
include receiving a signal for path loss estimation from a
transmission terminal, measuring reference signal received power
(RSRP) based on the signal for path loss estimation, and
transmitting a path loss estimation result report including the
RSRP to the transmission terminal.
[0048] In an embodiment, the RSRP may include at least one layer 1
RSRP (L1-RSRP), wherein the transmitting of the path loss
estimation result report including the RSRP to the transmission
terminal includes transmitting the at least one L1-RSRP via a
sidelink feedback channel (physical sidelink feedback channel
(PSFCH)) or a medium access control control element (MAC CE)
transmitted via a sidelink data channel (physical sidelink shared
channel (PSSCH)).
[0049] In an embodiment, the MAC CE may include the at least one
L1-RSRP, wherein, when the MAC CE includes a plurality of L1-RSRPs,
the MAC CE includes a user equipment (UE) ID.
[0050] In an embodiment, the transmitting of the path loss
estimation result report including the RSRP to the transmission
terminal may include transmitting the L1-RSRP every pre-configured
time or every pre-configured slots, after the signal for path loss
estimation is received, until a pre-configured timer expires, or
until a reporting stop command is received from the transmission
terminal.
[0051] In an embodiment, when information indicating that the path
loss estimation result report has not been received is received
from the transmission terminal, the path loss estimation method may
further include re-configuring the timer.
[0052] In an embodiment, the path loss estimation result report may
include layer 3 RSRP (L3-RSRP), wherein the transmitting of the
path loss estimation result report including the RSRP to the
transmission terminal includes transmitting the L3-RSRP through a
radio resource control (RRC) message transmitted via a sidelink
data channel (physical sidelink shared channel (PSSCH)).
[0053] In an embodiment, the signal for path loss estimation may
include at least one signal from among a sidelink synchronization
signal including at least one of a primary sidelink synchronization
signal (PSSS) and a secondary sidelink synchronization signal
(SSSS), a demodulation reference signal (DMRS) transmitted via at
least one of a sidelink broadcast channel (physical sidelink
broadcast channel (PSBCH)), a sidelink control channel (physical
sidelink control channel (PSCCH)), and a sidelink data channel
(physical sidelink shared channel (PSSCH)), and a reference signal
for supporting a sidelink operation.
[0054] In an embodiment, the transmitting of the path loss
estimation result report including the RSRP to the transmission
terminal may include transmitting the path loss estimation result
report periodically or aperiodically according to at least one of
configuration of a base station and sidelink control
information.
[0055] In an embodiment, the measuring of the RSRP based on the
signal for path loss estimation may include measuring
pre-configured transmission power, maximum transmission power of
the reception terminal, transmission power according to
configuration of a base station, and the RSRP for a signal for
downlink path loss estimation transmitted by the base station.
[0056] In an embodiment, the path loss estimation method may
further include receiving information on transmission power of the
signal for path loss estimation including at least one of offset
information between a configured reference signal and a
transmission power value of the signal for path loss estimation and
the transmission power value of the signal for path loss
estimation.
[0057] In an embodiment, the signal for path loss estimation and
the information on the transmission power of the signal for path
loss estimation may be received via the same channel or different
channels.
[0058] A transmission terminal according to an embodiment may
include a transceiver, a memory storing a path loss estimation
method program and data of the transmission terminal, and a process
configured to execute the program stored in the memory to transmit
a signal for path loss estimation to a reception terminal, receive
a path loss estimation result report from the reception terminal in
response to the signal for path loss estimation, configure
transmission power based on the path loss estimation result report,
and perform sidelink transmission with the reception terminal with
the configured transmission power.
[0059] A reception terminal according to an embodiment may include
a transceiver, a memory storing a path loss estimation method
program and data of the reception terminal, and a processor
configured to execute the program stored in the memory to receive a
signal for path loss estimation from a transmission terminal,
measure reference signal received power (RSRP) based on the signal
for path loss estimation, and transmit a path loss estimation
result report including the RSRP to the transmission terminal.
[0060] A path loss estimation method of a transmission terminal in
a wireless communication system according to another embodiment may
include receiving a signal for path loss estimation from a
reception terminal, estimating a path loss based on the signal for
path loss estimation, configuring transmission power based on the
path loss estimation result, and performing sidelink transmission
with the reception terminal with the configured transmission
power.
[0061] In an embodiment, the signal for path loss estimation may
include at least one from among a sidelink synchronization signal
including at least one of a primary sidelink synchronization signal
(PSSS) and a secondary sidelink synchronization signal (SSSS), a
demodulation reference signal (DMRS) transmitted via at least one
of a sidelink broadcast channel (physical sidelink broadcast
channel (PSBCH)), a sidelink control channel (physical sidelink
control channel (PSCCH)), and a sidelink data channel (physical
sidelink shared channel (PSSCH)), and a reference signal for
supporting a sidelink operation.
[0062] In an embodiment, the path loss estimation method may
further include transmitting a transmission request signal of the
signal for path loss estimation to the reception terminal, in at
least one case from among a case where a command for a transmission
request of the signal for path loss estimation is received from a
base station, a case where reference signal received power (RSRP)
measured by the transmission terminal for a signal for sidelink
path loss estimation transmitted by the base station is equal to or
greater than a configured threshold value or equal to or less than
a configured threshold value, and a case where the transmission
terminal determines that the signal for path loss estimation needs
to be transmitted.
[0063] In an embodiment, the transmitting of the transmission
request signal of the signal for path loss estimation to the
reception terminal may include configuring, as transmission power
of the transmission request signal of the signal for path loss
estimation, at least one of pre-configured transmission power,
maximum transmission power of the transmission terminal,
transmission power according to configuration of a base station,
and transmission power determined based on RSRP measured by the
transmission terminal for a signal for downlink path loss
estimation transmitted by the base station.
[0064] In an embodiment, the path loss estimation method may
further include receiving information on transmission power of the
signal for path loss estimation including at least one of offset
information between a configured reference signal and a
transmission power value of the signal for path loss estimation and
the transmission power value of the signal for path loss
estimation.
[0065] In an embodiment, the signal for path loss estimation and
the information on the transmission power of the signal for path
loss estimation may be received via the same channel or different
channels.
[0066] A path loss estimation method of a reception terminal in a
wireless communication system according to another embodiment may
include transmitting a signal for path loss estimation to a
transmission terminal and performing sidelink transmission with the
transmission terminal.
[0067] In an embodiment, the signal for path loss estimation may
include at least one signal from among a sidelink synchronization
signal including at least one of a primary sidelink synchronization
signal (PSSS) and a secondary sidelink synchronization signal
(SSSS), a demodulation reference signal (DMRS) transmitted via at
least one of a sidelink broadcast channel (physical sidelink
broadcast channel (PSBCH)), a sidelink control channel (physical
sidelink control channel (PSCCH)), and a sidelink data channel
(physical sidelink shared channel (PSSCH)), and a reference signal
for supporting a sidelink operation.
[0068] In an embodiment, the transmitting of the signal for path
loss estimation to the transmission terminal may include
transmitting the signal for path loss estimation to the
transmission terminal, in at least one case from among a case where
a command for transmission of the signal for path loss estimation
is received from a base station, a case where reference signal
received power (RSRP) measured by the reception terminal for a
signal for downlink path loss estimation transmitted by the base
station is equal to or greater than a pre-configured threshold
value or equal to or less than a configured threshold value, a case
where the reception terminal determines that the signal for path
loss estimation needs to be transmitted, and a case where a
transmission request signal of the signal for path loss estimation
is received from the transmission terminal.
[0069] In an embodiment, the transmitting of the signal for path
loss estimation to the transmission terminal may include
configuring, as transmission power of the signal for path loss
estimation, at least one of pre-configured transmission power,
maximum transmission power of the reception terminal, transmission
power according to configuration of a base station, transmission
power determined based on RSRP measured by the reception terminal
for a signal for downlink path loss estimation transmitted by the
base station, and transmission power determined based on RSRP
measured by the reception terminal for a transmission request
signal of the signal for path loss estimation received from the
transmission terminal.
[0070] In an embodiment, the path loss estimation method may
further include transmitting, to the transmission terminal,
information on the transmission power of the signal for path loss
estimation including at least one of offset information between a
configured reference signal and a transmission power value of the
signal for path loss estimation and the transmission power value of
the signal for path loss estimation.
[0071] In an embodiment, the signal for path loss estimation and
the information on the transmission power of the signal for path
loss estimation may be transmitted via the same channel or
different channels.
[0072] In an embodiment, the performing of the sidelink
transmission with the transmission terminal may include receiving
at least one of sidelink control information and sidelink data from
the transmission terminal.
[0073] A transmission terminal according to another embodiment may
include a transceiver, a memory storing a path loss estimation
method program and data of the transmission terminal, and a
processor configured to execute the program stored in the memory to
receive a signal for path loss estimation from a reception
terminal, estimate a path loss based on the signal for path loss
estimation, configure transmission power based on a path loss
estimation result, and perform sidelink transmission with the
reception terminal with the configured transmission power.
[0074] A reception terminal according to another embodiment may
include a transceiver, a memory storing a path loss estimation
method program and data of the reception terminal, and a processor
configured to execute the program stored in the memory to transmit
a signal for path loss estimation to a transmission terminal and
perform sidelink transmission with the transmission terminal.
[0075] Hereinafter, embodiments of the present disclosure will be
described in detail with reference to the accompanying
drawings.
[0076] In the following description of embodiments, descriptions of
techniques that are well known in the art and not directly related
to the present disclosure are omitted. This is to clearly convey
the gist of the present disclosure by omitting an unnecessary
description.
[0077] For the same reason, some elements in the drawings are
exaggerated, omitted, or schematically illustrated. Also, the size
of each element does not entirely reflect the actual size of the
element. In the drawings, the same or corresponding elements are
denoted by the same reference numerals.
[0078] The advantages and features of the present disclosure and
methods of achieving them will become apparent with reference to
embodiments of the present disclosure described in detail below
along with the attached drawings. The present disclosure may,
however, be embodied in many different forms and should not be
construed as limited to embodiments of the present disclosure set
forth herein; rather these embodiments of the present disclosure
are provided so that this disclosure will be thorough and complete,
and will fully convey the scope of the present disclosure to one of
ordinary skill in the art, and the present disclosure is defined
only by the accompanying claims. In the specification, the same
reference numerals denote the same elements.
[0079] In this case, it will be understood that each block of
flowchart illustrations and combinations of blocks in the flowchart
illustrations may be implemented by computer program instructions.
Because these computer program instructions may be loaded into a
processor of a general-purpose computer, a special purpose
computer, or a programmable data processing device, the
instructions, which are executed via the processor of the computer
or another programmable data processing device, generate means for
implementing functions described in the flowchart block(s). Because
these computer program instructions may also be stored in a
computer-usable or computer-readable memory that may direct a
computer or another programmable data processing device to function
in a particular manner, the instructions stored in the
computer-usable or computer-readable memory may produce
manufacturing items including instruction means that implement the
functions described in the flowchart block(s). Because the computer
program instructions may also be loaded into a computer or another
programmable data processing device, a series of operational steps
may be performed on the computer or other programmable device to
produce a computer implemented process, and thus the instructions
executed on the computer or other programmable device may provide
steps for implementing the functions described in the flowchart
block(s).
[0080] Also, each block of the flowchart illustrations may
represent a module, segment, or portion of code, which includes one
or more executable instructions for implementing specified logical
function(s). It should also be noted that in some alternative
implementations, functions noted in blocks may occur out of order.
For example, two blocks shown in succession may actually be
executed substantially concurrently or the blocks may sometimes be
executed in a reverse order, depending upon the functionality
involved.
[0081] In this case, the term `.about.unit` used in the present
embodiment refers to a software or hardware component, such as a
field-programmable gate array (FPGA) or an application-specific
integrated circuit (ASIC), which performs certain tasks. However,
the term `.about.unit` is not limited to software or hardware. The
term `.about.unit` may be configured to be in an addressable
storage medium or configured to operate one or more processors.
Accordingly, `.about.unit` may include, by way of example,
components such as software components, object-oriented software
components, class components, and task components, processes,
functions, attributes, procedures, and subroutines, segments of
program code, drivers, firmware, microcode, circuitry, data,
databases, data structures, tables, arrays, and variables. The
functionality provided in components and `.about.units` may be
combined into fewer components and `.about.units`, or may be
further separated into additional components and `.about.units`.
Further, components and `.about.units` may be implemented to
operate one or more central processing units (CPUs) in a device or
a secure multimedia card. Also, a `.about.unit` in an embodiment
may include one or more processors.
[0082] Also, terms for identifying access nodes, terms denoting
network entities, terms denoting messages, terms denoting
interfaces between network entities, terms denoting various types
of identification information, etc. used herein are exemplified for
convenience of description. Accordingly, the terms used in the
present disclosure are not limited and other terms denoting targets
having the same technical meanings may be used.
[0083] In the present disclosure, for convenience of description,
the present disclosure uses terms and names defined in standards
regarding 5.sup.th generation (5G), new radio (NR), or long term
evolution (LTE) systems. However, the present disclosure is not
limited by such terms and names, and may be equally applied to
systems complying with other standards.
[0084] While a description will be focused on a communication
standard specified by the 3.sup.rd generation partnership project
(3GPP), when embodiments of the present disclosure are described in
detail, a main subject matter to be claimed in the specification is
also applicable to other communication systems and services having
a similar technical background without significantly departing from
a range disclosed herein, as will be obvious to one of ordinary
skill in the art.
[0085] In the present disclosure, a transmission terminal does not
refer a terminal that transmits a signal for path loss estimation,
but refers to a terminal that transmits sidelink data and control
information. In the present disclosure, a reception terminal does
not refer to a terminal that receives a signal for path loss
estimation, but refers to a terminal that receives sidelink data
and control information.
[0086] FIG. 1 is a view for describing a vehicle-to-everything
(V2X) system to which a disclosed embodiment is applied.
[0087] (a) of FIG. 1 shows an example in which all V2X user
equipments (UEs) UE-1 and UE-2 are located in coverage of a base
station gNB/eNB/RSU (in-coverage scenario). All of the V2X UEs UE-1
and UE-2 may receive data and control information from the base
station gNB/eNB/RSU through a downlink (DL) or may transmit data
and control information to the base station through an uplink (UL).
In this case, the data and control information may be data and
control information for V2X communication, or data and control
information for general cellular communication other than V2X
communication. Also, in (a) of FIG. 1, the V2X UEs UE-1 and UE-2
may transmit and receive data and control information for V2X
communication through a sidelink (SL).
[0088] (b) of FIG. 1 shows an example in which the V2X UE UE-1 is
located in the coverage of the base station gNB/eNB/RSU and the V2X
UE UE-2 is located out of the coverage of the base station
gNB/eNB/RSU (partial coverage scenario). The V2X UE UE-1 located in
the coverage of the base station gNB/eNB/RSU may receive data and
control information from the base station gNB/eNB/RSU through a
downlink (DL) or transmit data and control information to the base
station gNB/eNB/RSU through an uplink (UL). The V2X UE UE-2 located
out of the coverage of the base station gNB/eNB/RSU may not receive
data and control information from the base station gNB/eNB/RSU
through the downlink and may not transmit data and control
information to the base station gNB/eNB/RSU through the uplink. The
V2X UE UE-2 may transmit and receive data and control information
for V2X communication through the sidelink (SL).
[0089] (c) of FIG. 1 shows an example in which all of the V2X UEs
UE-1 and UE2 are located out of the coverage of the base station
gNB/eNB/RSU (out-of-coverage scenario). Accordingly, the V2X UEs
UE-1 and UE-2 may not receive data and control information from the
base station gNB/eNB/RSU through the downlink (DL) and may not
transmit data and control information to the base station
gNB/eNB/RSU through the uplink (UL). The V2X UEs UE-1 and UE-2 may
transmit and receive data and control information for V2X
communication through the sidelink (SL).
[0090] (d) of FIG. 1 shows an example in which a V2X transmission
UE and a V2X reception UE are connected to different base stations
gNBs/eNBs/RSUs (a radio resource control (RRC) connected state) or
are camped (an RRC-disconnected state, i.e., an RRC idle state)
(inter-cell V2X communication scenario). In this case, the V2X UE
UE-1 may be a V2X transmission UE and the V2X UE UE-2 may be a V2X
reception UE. Alternatively, the V2X UE UE-1 may be a V2X reception
UE and the V2X UE UE-2 may be a V2X transmission UE. The V2X UE
UE-1 may receive a V2X dedicated system information block (SIB)
from a base station to which the V2X UE UE-1 is connected (or in
which the V2X UE UE-1 is camped), and the V2X UE UE-2 may receive a
V2X dedicated SIB from another base station to which the V2X UE
UE-2 is connected (or in which the V2X UE UE-2 is camped). In this
case, information of the V2X dedicated SIB received by the V2X UE
UE-1 and information of the V2X dedicated SIB received by the V2X
UE UE-2 may be different from each other. Accordingly, to perform
V2X communication between UEs located in different cells, the
information needs to be united.
[0091] While a description has been made with reference to FIG. 1
by using a V2X system including two UEs UE-1 and UE-2 as an example
for convenience, various numbers of UEs may join the V2X system
without being limited to the description. The uplink (UL) and the
downlink (DL) with the base station gNB/eNB/RSU and the V2X UEs
UE-1 and UE-2 may be referred to as Uu interfaces, and the sidelink
(SL) between the V2X UEs UE-1 and UE-2 may be referred to as a PC5
interface. Accordingly, in the present disclosure, these terms may
be used interchangeably.
[0092] Meanwhile, in the present disclosure, a UE may refer to a
vehicle supporting vehicle-to-vehicle (V2V) communication, a
vehicle or a handset of a pedestrian (e.g., a smartphone)
supporting vehicle-to-pedestrian (V2P) communication, a vehicle
supporting vehicle-to-network (V2N) communication, or a vehicle
supporting vehicle-to-infrastructure (V2I) communication. Also, in
the present disclosure, the UE may refer to a road side unit (RSU)
having a UE function, an RSU having a base station function, or an
RSU having a part of the UE function and a part of the base station
function.
[0093] FIG. 2 is a view for describing a V2X communication method
performed through a sidelink.
[0094] As shown in (a) of FIG. 2, a transmission UE and a reception
UE may perform one-to-one communication, which may be referred to
as unicast communication.
[0095] As shown in (b) of FIG. 2, a transmission UE and a reception
UE may perform one-to-many communication, which may be referred to
as groupcast or multicast communication. In (b) of FIG. 2, UE-1,
UE-2, and UE-3 perform groupcast communication by forming one group
(group A), and UE-4, UE-5, UE-6, and UE-7 perform groupcast
communication by forming another group (group B). Each UE performs
groupcast communication only in a group to which the UE belongs,
and communication is not performed between different groups.
Although two groups are formed in (b) of FIG. 2, a greater number
of groups may be formed without being limited to the
illustration.
[0096] Meanwhile, although not shown in FIG. 2, V2X UEs may perform
broadcast communication. In broadcast communication, all V2X UEs
receive data and control information transmitted by a V2X
transmission UE through a sidelink. For example, in (b) of FIG. 2,
when it is assumed that the V2X UE UE-1 is a transmission UE for
broadcast communication, all UEs UE-2, UE-3, UE-4, UE-5, UE-6, and
UE-7 may receive data and control information transmitted by the
V2X UE UE-1.
[0097] FIG. 3 is a diagram for describing a method by which a UE
estimates a downlink path loss (PL) in an existing cellular
system.
[0098] A UE TX UE may receive a parameter configuration for
estimating a downlink path loss and a signal for estimating a path
loss from a base station eNB/gNB. The UE TX UE may receive a path
loss signal transmitted by the base station eNB/gNB for downlink
path loss estimation, may measure reference signal received power
(RSRP), and may measure a downlink path loss by using [Equation
1].
downlink path loss=transmission power of base station signal-RSRP
measured by UE [Equation 1]
[0099] In this case, transmission power of a base station signal
may be transmission power of a signal for downlink path loss
estimation transmitted by the base station, and a signaling method
may vary according to a type of the signal. For example, when an
estimation signal is a cell-specific reference signal (CRS), the
transmission power of the base station signal may refer to
transmission power of the CRS, and may be transmitted to the UE
through a parameter referenceSignalPower of system information.
When the estimation signal is a synchronization signal block (SSB),
the transmission power of the base station signal may refer to
transmission power of a demodulation reference signal (DMRS)
transmitted via a physical broadcast channel (PBCH) and a secondary
synchronization signal (SSS), and may be transmitted to the UE
through a parameter ss-PBCH-BlockPower of the system information.
When the estimation signal is a channel state information-reference
signal (CSI-RS), the base station may transmit information on
transmission power of the CSI-RS to the UE through a parameter
powerControlOffsetSS of UE dedicated RRC information. In this case,
powerControlOffsetSS may refer to a transmission power difference
(offset) between the CSI-RS and the SSB.
[0100] The UE TX UE may configure a transmission power value of
uplink data and control information based on an estimated downlink
path loss value and may perform uplink transmission.
[0101] FIG. 4 is a diagram for describing a method of estimating an
inter-UE sidelink path loss, according to a disclosed
embodiment.
[0102] In FIG. 3, a base station eNB/gNB may be considered as a
receiver that receives uplink data and control information from a
UE. That is, the receiver (base station) may transmit a signal for
path loss estimation and transmission power of the signal for path
loss estimation to a transmitter (UE), and the transmitter (UE) may
configure a transmission power value for uplink data and control
information transmission based on a path loss value estimated by
the transmitter (UE) and may perform uplink transmission to the
receiver (base station).
[0103] A similar operation may be used for inter-UE sidelink path
loss estimation. For example, as shown in (a) of FIG. 4, a
reception (RX) UE may transmit a signal for sidelink path loss
estimation and information on transmission power to a transmission
(TX) UE, and the TX UE may estimate a sidelink path loss value by
using the signal and the information. The RX UE may configure
transmission power of sidelink data and control information based
on the estimated path loss value, and may perform sidelink
transmission to the TX UE. In more detail, in (a) of FIG. 4, the RX
UE may transmit a signal for path loss estimation and information
on transmission power of the signal to the TX UE. The TX UE may
receive the signal for path loss estimation, may measure RSRP, and
may estimate a path loss by using [Equation 1]. The TX UE may
configure sidelink transmission power based on the estimated path
loss value, and may transmit sidelink control information and data
information to the RX UE.
[0104] As shown in (b) of FIG. 4, the RX UE may transmit a signal
for path loss estimation in response to a request of the TX UE. In
(b) of FIG. 4, the TX UE may transmit a request for transmission of
a signal for path loss estimation to the RX UE, and the RX UE
receiving the request may transmit the signal for path loss
estimation to the TX UE. In this case, the RX UE may transmit
information on transmission power of the signal for path loss
estimation to the TX UE. The TX UE may measure RSRP through the
signal for path loss estimation and may estimate a path loss by
using [Equation 1]. The TX UE may configure sidelink transmission
power based on the estimated path loss value, and may transmit
sidelink control information and data information to the RX UE.
[0105] In the present disclosure, a TX UE does not refer to a UE
that transmits a signal for path loss estimation, but refers to a
UE that transmits sidelink data and control information. Also, an
RX UE does not refer to a UE that receives a signal for path loss
estimation, but refers to a UE that receives sidelink data and
control information.
[0106] FIG. 5 is a diagram illustrating a method of estimating an
inter-UE sidelink path loss, according to another disclosed
embodiment.
[0107] Unlike in FIG. 4, in FIG. 5, a TX UE transmits a signal for
path loss estimation, and an RX UE estimates a path loss. Like in
FIG. 4, in FIG. 5, a signal for path loss estimation transmitted by
the TX UE may be transmitted without a request of the RX UE ((a) of
FIG. 5), or may be transmitted in response to a request of the TX
UE ((b) of FIG. 5). In more detail, in (a) of FIG. 5, the TX UE may
transmit a signal for path loss estimation to the RX UE and may
transmit information on transmission power of the signal. The RX UE
may measure RSRP by using the signal for path loss estimation and
may estimate a path loss by using [Equation 1]. The RX UE may
report information on the path loss value estimated by the RX UE to
the TX UE. The TX UE may configure sidelink transmission power
based on the information on the path loss value reported from the
RX UE, and may transmit sidelink control information and data
information to the RX UE.
[0108] In (b) of FIG. 5, the RX UE may transmit a request for
transmission of a signal for path loss estimation to the TX UE, and
the TX UE receiving the request may transmit the signal for path
loss estimation to the RX UE. In this case, the TX UE may transmit
information on transmission power of the signal for path loss
estimation to the RX UE. The RX UE may measure RSRP through the
signal for path loss estimation and may estimate a path loss by
using [Equation 1]. The RX UE may report information on the path
loss value estimated by the RX UE to the TX UE. The TX UE may
configure sidelink transmission power based on the information on
the path loss value reported from the RX UE and may transmit
sidelink control information and data information to the RX UE.
[0109] A signal for path loss estimation described with reference
to FIGS. 4 and 5 may include at least one of the following signals.
[0110] Sidelink synchronization signal, which refers to a signal
for obtaining time/frequency synchronization of a sidelink between
UEs and may include a primary sidelink synchronization signal
(PSSS) and a secondary sidelink synchronization signal (SSSS). In
path loss estimation, only one of the PSSS and the SSSS may be
used, or both the PSSS and the SSSS may be used. When only of the
two signals is used, UEs may be pre-configured with information on
which signal from among the PSSS and the SSSS is to be used to
estimate a path loss. When both the PSSS and the SSSS are used, a
UE receiving a path loss signal may measure RSRP by using a
time/frequency average value of the PSSS and the SSSS. [0111]
Demodulation reference signal (DMRS) transmitted via a sidelink
broadcast channel, similar to a broadcast channel (a physical
broadcast channel (PBCH)) transmitted by a base station to a UE in
a general cellular communication, a sidelink broadcast channel (a
physical sidelink broadcast channel (PSBCH)) for transmitting
master information for sidelink communication may exist in inter-UE
communication. In this case, a DMRS may exist in the PSBCH for
channel estimation to demodulate and decode the PSBCH. UEs may
measure RSRP by using the DMRS and may estimate a path loss value.
In this case, a transmission power value of the PSBCH may be a
fixed value, and all sidelink UEs may be configured with the
transmission power value of the PSBCH from a base station through
RRC signaling, or may be pre-recognized (pre-configured) in the
absence of the base station. The same transmission power as that of
a PSSS/SSSS may be used as the transmission power value of the
PSBCH, or the transmission power value of the PSBCH may have a
fixed offset value and a transmission power value of the PSSS/SSSS.
When the base station configures the transmission power value of
the PSBCH, the base station may configure the transmission power
value of the PSSS/SSSS in a UE, and the UE may calculate the
transmission power value of the PSBCH by using the fixed offset
value. Alternatively, the base station may configure the
transmission power value of the PSSS/SSSS and the offset value
through system information or a UE dedicated RRC message. [0112]
DMRS transmitted via a sidelink control channel or data channel, a
sidelink TX UE may transmit a sidelink control channel (a physical
sidelink control channel (PSCCH)) or a sidelink data channel (a
physical sidelink shared channel (PSSCH)) to a sidelink RX UE. In
this case, a DMRS may exist in each of the PSCCH and the PSSCH, and
the sidelink RX UE may measure RSRP by using the DMRS. In this
case, the RSRP may be measured by using only one of the DMRS of the
PSCCH and the DMRS of the PSSCH, or may be measured by using both
the DMRS of the PSCCH and the DMRS of the PSSCH. When the RSRP is
measured by using only one, information on which channel's DMRS
from among the two is to be used may be pre-defined. When both the
DMRS transmitted via the PSCCH and the DMRS transmitted via the
PSSCH are used, different RSRP measurement operations may be
considered according to a multiplexing method of the PSCCH and the
PSSCH. That is, the PSCCH and the PSSCH may be time-divided or
frequency-divided and transmitted. When the PSCCH and the PSSCH are
time-divided and transmitted, the sidelink RX UE may measure the
RSRP by obtaining an average of the DMRS of the PSCCH and the DMRS
of the PSSCH in a time domain. When the PSCCH and the PSSCH are
frequency-divided and transmitted, the sidelink RX UE may measure
the RSRP by obtaining an average of the DMRS of the PSCCH and the
DMRS of the PSSCH in a frequency domain. Alternatively, the RSRP
may be measured by obtaining an average in both the time domain and
the frequency domain. Information on how the sidelink RX UE is to
measure the RSRP (e.g., an average in the time domain, an average
in the frequency domain, or an average in both the time/frequency
domains) may be pre-determined, or may be notified by the sidelink
TX UE to the sidelink RX UE via a PSBCH. [0113] New reference
signal for supporting a sidelink operation, a sidelink sounding
reference signal (SRS), a sidelink channel state
information-reference signal (CSI-RS), or a sidelink phase tracking
reference signal (PTRS) may be defined for a purpose similar to
that of existing cellular communication.
[0114] FIG. 6 is a diagram for describing a method of transmitting
and receiving a path loss measurement signal to estimate a sidelink
path loss, according to a disclosed embodiment.
[0115] FIG. 6 is a detailed diagram illustrating a process of (a)
of FIG. 4. In the present disclosure, a base station may be a base
station that supports both V2X communication and general cellular
communication, or a road side unit (RSU) that supports only V2X
communication. Accordingly, unless otherwise specified in the
present disclosure, the base station and the RSU may be used for
the same concept and may be interchangeably used.
[0116] Also, in FIG. 6, UL synchronization and RRC connection setup
and command are each marked by a dashed line. In the present
disclosure, a procedure or an operation marked by a dashed line may
be an optional procedure or an optional operation. That is, a
procedure or an operation marked by a dashed line may be performed
or may not be performed. This is the same not only in FIG. 6 but
also in other drawings below.
[0117] V2X UEs in coverage of the base station may perform downlink
synchronization and may obtain system information. In this case,
the downlink synchronization may be performed through a primary
synchronization signal/secondary synchronization signal (PSS/SSS)
received from the base station, or may be performed through a
synchronization signal received from a global navigation satellite
system (GNSS). The V2X UEs performing the downlink synchronization
may obtain system information related to V2X through a V2X
dedicated system information block (SIB) transmitted by the base
station gNB/RSU. Also, the V2X UEs in the coverage may perform
uplink synchronization through a random access procedure with the
base station and may perform an RRC connection procedure. In this
case, the uplink synchronization and the RRC connection procedure
may be performed by only one of a transmission UE or a reception
UE, or may be performed by both the transmission UE and the
reception UE.
[0118] Information on which UE from among the transmission UE and
the reception UE is to perform the uplink synchronization and the
RRC connection procedure may vary according to a transmission mode
of sidelink control information/data information, a sidelink path
loss estimation procedure, a signaling method, etc. For example, as
shown in FIG. 6, in a mode in which the base station transmits a
command for transmission of a path loss signal to a V2X reception
UE, the reception UE may have to perform the uplink synchronization
and the RRC connection procedure with the base station. Also, as
shown in FIG. 7, in a mode in which the base station transmits a
command for transmission of a path loss signal to a V2X
transmission UE, the transmission UE may have to perform the uplink
synchronization and the RRC connection procedure with the base
station.
[0119] Although not shown in FIGS. 6 and 7, when the base station
transmits a command for transmission of a path loss signal to the
V2X reception UE and transmits a command for reception of a path
loss signal to the V2X transmission UE, both the reception UE and
the transmission UE may have to perform the uplink synchronization
and the RRC connection procedure with the base station according to
a signaling method. For example, when a command of the base station
is transmitted to the V2X transmission UE and the V2X reception UE
through downlink control information (DCI), a medium access control
control element (MAC CE), or a UE dedicated RRC message, the V2X
transmission UE and the V2X reception UE may perform the uplink
synchronization and the RRC connection procedure with the base
station. When a command of the base station is transmitted to the
V2X transmission UE and the V2X reception UE through V2X system
information, the V2X transmission UE and the V2X reception UE may
not perform the uplink synchronization and the RRC connection
procedure with the base station.
[0120] In FIG. 6, a reception UE may refer to a UE that receives
sidelink control information and data information, and a
transmission UE may refer to a UE that transmits sidelink control
information and data information. Accordingly, the reception UE and
the transmission UE in FIG. 6 may not be related to transmission
and reception of a path loss signal.
[0121] A V2X transmission UE or a V2X reception UE performing
downlink synchronization or uplink synchronization and RRC
connection configuration with the base station may perform sidelink
configuration for unicast communication. The unicast link
configuration may be performed in a higher layer (e.g., an
application layer), and as shown in FIG. 6, the unicast link
configuration may be performed between the V2X transmission UE that
is to transmit V2X control information/data information in a
unicast method and the V2X reception UE that is to receive the V2X
control information/data information in the unicast method. Also,
although not shown in FIG. 6, the base station may engage in the
unicast link configuration. For example, the V2X transmission UE
may transmit a request for the unicast link configuration to the
base station, and the base station may transmit a response to the
request to the V2X reception UE. Also, the base station may
transmit a confirmation for the unicast link configuration to the
V2X transmission UE and the V2X reception UE. However, as described
above, because this procedure may be performed in the higher layer,
the procedure may not be recognized by a physical layer and a MAC
layer.
[0122] As shown in FIG. 6, the base station may transmit a command
for transmission of a signal for path loss estimation to the V2X
reception UE. In this case, the command of the base station may be
transmitted to the V2X reception UE through UE-specific DCI (or
group common DCI) for a sidelink or through a MAC CE or a
UE-specific RRC message. When the command for transmission of the
signal for path loss estimation is transmitted through the
UE-specific DCI or the group common DCI from the base station, the
DCI may use a radio network temporary identifier (RNTI) different
from UE-specific DCI or group common DCI used in existing cellular
communication for distinguishment from existing cellular
communication.
[0123] Also, unlike in FIG. 6, the V2X reception UE may transmit
the signal for path loss estimation to the V2X transmission UE
after unicast link configuration without the command of the base
station. For example, the V2X reception UE may start a timer at a
point of time when a request for unicast link configuration is
received from the base station or the V2X transmission UE or at a
point of time when the unicast link configuration succeeds, and may
transmit the signal for path loss estimation to the V2X
transmission UE at a point of time when the timer expires.
Likewise, the V2X transmission UE may start a timer from a point of
time when a request for unicast link configuration is transmitted
or from a point of time when the unicast link configuration
succeeds, and may expect to receive the signal for path loss
estimation from the V2X reception UE at a point of time when the
timer expires. In another example, the V2X reception UE may
transmit the signal for path loss estimation after a certain period
of time (e.g., after [x] subframes, [x] slots, or [x] ms) from a
point of time when unicast link configuration succeeds. Likewise,
the V2X transmission UE may receive the signal for path loss
estimation after a certain period of time (e.g., [x] subframes, [x]
slots, or [x] ms) from a point of time when unicast link
configuration succeeds.
[0124] In another example where the V2X reception UE transmits the
signal for path loss estimation without the command of the base
station, when an RSRP value measured by the V2X reception UE with
the base station is equal to or greater than (or greater than) a
specific threshold value configured by the base station or is equal
to or less than (or less than) a specific threshold value, the V2X
reception UE may transmit the signal for path loss estimation to
the V2X transmission UE. In this case, the base station may
configure the RSRP threshold value in the V2X reception UE through
a system transmission block for V2X (V2X SIB) or a UE-specific
RRC/common RRC message for V2X. In another example, when a
variation of the RSRP value with the base station is equal to or
greater than (or greater than) a specific threshold value
configured by the base station, the V2X reception UE may transmit
the signal for path loss estimation to the V2X transmission UE.
Although the V2X reception UE satisfies a condition for the RSRP
threshold value configured by the base station, when the base
station sends a command for stopping transmitting the signal for
path loss estimation, the V2X reception UE may stop transmitting
the signal for path loss estimation.
[0125] In another example where the V2X reception UE transmits the
signal for path loss estimation without the command of the base
station, when a modulation order of V2X data information received
by the V2X reception UE is equal to or less than, or less than a
certain level, the V2X reception UE may transmit the signal for
path loss estimation. For example, when the modulation order of the
V2X data information received by the V2X reception UE is equal to
or less than 16-quadrature amplitude modulation (QAM) (or is
quadrature phase-shift keying (QPSK) less than 16-QAM), the V2X
reception UE may transmit the signal for path loss estimation to
the V2X transmission UE. In another example, when a transport block
(TBS) size of the V2X data information received by the V2X
reception UE is equal to or greater than, or greater than specific
bits, the V2X reception UE may transmit the signal for path loss
estimation to the V2X transmission UE. For example, when the TBS
size of the received V2X data information is equal to or greater
than (or greater than) y bits, the V2X reception UE may transmit
the signal for path loss estimation to the V2X transmission UE. In
another example, when an aggregation level of a V2X control channel
received by the V2X reception UE is equal to or greater than, or
greater than a certain level, the V2X reception UE may transmit the
signal for path loss estimation (e.g., when the aggregation level
is equal to or greater than 8, or is equal to 16 that is greater
than 8).
[0126] In another example where the V2X reception UE transmits the
signal for path loss estimation without the command of the base
station to the V2X transmission UE, when an RSRP value of a
sidelink channel previously measured by the V2X reception UE is
equal to or greater than (or greater than) a specific threshold
value configured by the base station, or is equal to or less than
(or less than) a specific threshold value, the V2X reception UE may
transmit the signal for path loss estimation to the V2X
transmission UE. In this case, the base station may configure the
RSRP threshold value of the sidelink channel in the V2X reception
UE through a system transmission block for V2X (V2X SIB) or a
UE-specific RRC/common RRC message for V2X. In this case, when the
RSRP value of the sidelink channel satisfies a specific threshold
value condition configured by the base station at least once, the
V2X reception UE may transmit the signal for path loss estimation
to the V2X transmission UE. Alternatively, when the RSRP value of
the sidelink channel satisfies the specific threshold value
condition configured by the base station X times (or more), the V2X
reception UE may transmit the signal for path loss estimation to
the V2X transmission UE. In this case, X may be pre-defined, or may
be configured by the base station. In another example, when a
variation of the RSRP value of the sidelink channel is equal to or
greater than (or greater than) a specific threshold value
configured by the base station, the V2X reception UE may transmit
the signal for path loss estimation to the V2X transmission UE.
Even when the V2X reception UE satisfies a condition for the RSRP
threshold value of the sidelink channel, which is configured by the
base station, when the base station transmits a command for
stopping transmitting the signal for path loss estimation, the V2X
reception UE may stop transmitting the signal for path loss
estimation. In another example, a threshold value for the RSRP
value of the sidelink channel or the variation of the RSRP value of
the sidelink channel may be pre-configured without signaling from
the base station.
[0127] In the above examples where the V2X reception UE transmits
the signal for path loss estimation, V2X reception UEs may refer to
UEs having a capability to transmit a signal for V2X path loss
estimation. Accordingly, from among UEs having the capability, V2X
reception UEs satisfying the above conditions may transmit the
signal for path loss estimation.
[0128] As shown in FIG. 6, the base station may transmit a command
for transmission of the signal for path loss estimation to the V2X
reception UE, and in this case, whether the V2X reception UE is
capable of transmitting the signal for path loss estimation may be
a V2X UE capability. That is, the base station may identify V2X UEs
having a capability to transmit the signal for path loss estimation
through a capability negotiation procedure with the V2X UEs, and
may transmit the command for transmission of a signal for V2X path
loss estimation only to UEs having a capability to transmit the
signal for V2X path loss estimation. In this case, the command of
the base station may be transmitted to the V2X reception UE through
UE-specific DCI (or group common DCI) for a sidelink or through a
UE-specific RRC message. The V2X reception UE receiving the command
for transmission of the signal for path loss estimation may
transmit the signal for path loss estimation to the V2X
transmission UE. Alternatively, when the above condition is
satisfied without the command of the base station (e.g., expiration
of a timer, RSRP with the base station, or a modulation order), V2X
reception UEs having a capability to transmit the signal for path
loss estimation may transmit the signal for path loss estimation to
the V2X transmission UE. In this case, the V2X transmission UE may
obtain information on transmission power of the signal for path
loss estimation by using at least one of the following various
methods.
[0129] A method of transmitting information on transmission power
of a signal for path loss estimation according to an embodiment
will be described below. [0130] Base station transmits information
on transmission power of a signal for path loss estimation to a V2X
transmission UE through RRC signaling [0131] A base station may
transmit information on transmission power of a signal for path
loss estimation to a V2X transmission UE through RRC signaling. In
detail, the base station may transmit transmission power
information of the signal for path loss estimation to all V2X UEs
in cell coverage through a V2X dedicated system information block
V2X SIB. In this case, the V2X transmission UE may receive the
information even when there is no RRC connection configuration with
the base station. In another example, the base station may transmit
the information on the transmission power of the signal for path
loss estimation transmitted by a V2X reception UE to the V2X
transmission UE through UE dedicated RRC or UE common RRC
signaling. In this case, the V2X transmission UE may have to
perform RRC connection configuration with the base station. As
described above, when the V2X transmission UE directly receives the
information on the transmission power of the signal for path loss
estimation from the base station, the V2X reception UE may not
transmit the information on the transmission power of the signal
for path loss estimation to the V2X transmission UE. [0132] A V2X
system may support at least two modes according to whether the V2X
transmission UE performs RRC connection configuration: mode (Mode
A) in which the V2X transmission UE may operate without RRC
connection configuration, and mode (Mode B) in which the V2X
transmission UE may operate only with RRC connection configuration.
In Mode A and Mode B, the V2X reception UE may operate even with no
RRC connection. A new mode may be defined in the V2X system (Mode
C), and in Mode C, both the V2X transmission UE and the reception
UE may operate only with the RRC connection configuration.
Information on which mode from among the above modes is to be used
may be notified by the base station to all V2X UEs existing in
coverage of the base station through system information. In another
example, each mode may be mapped to a resource pool or a resource
of the V2X system. That is, a resource or a resource pool for Mode
A, a resource or a resource pool for Mode B, and a resource or a
resource pool for Mode C may exist, and each UE may derive which
mode is to be used to operate from a time/frequency resource or
resource pool received from the base station. [0133] V2X reception
UE transmits information on transmission power of a signal for path
loss estimation to a V2X transmission UE via a sidelink broadcast
channel [0134] A V2X reception UE may transmit information on
transmission power of a signal for path loss estimation to a V2X
transmission UE via a sidelink broadcast channel. In this case, the
information on the transmission power transmitted by the V2X
reception UE may be information received from a base station. For
example, as shown in (b) of FIG. 1, a scenario in which the V2X
reception UE exists in coverage of the base station and the V2X
transmission UE exists out of the coverage of the base station may
be considered. In this situation, the V2X transmission UE may not
receive system information and RRC information from the base
station. Accordingly, the V2X reception UE existing in the coverage
of the base station may transmit the information on the
transmission power of the signal for path loss estimation through a
sidelink broadcast channel so that the V2X transmission UE existing
out of the coverage of the base station estimates a sidelink path
loss. [0135] In another example, as shown in (d) of FIG. 1, the V2X
reception UE and the V2X transmission UE may exist in different
cells. That is, a V2X reception UE UE-1 may exist in coverage of a
base station 1, and a V2X transmission UE UE-2 may exist in
coverage of a base station 2. In this case, the V2X reception UE
UE-1 existing in the coverage of the base station 1 may transmit
the information on the transmission power of the signal for path
loss estimation to the V2X transmission UE UE-2 existing in the
coverage of the base station 2 via a sidelink broadcast channel.
[0136] The V2X reception UE may transmit transmission power
information determined by the V2X reception UE itself via a
sidelink broadcast channel, without the information on the
transmission power received from the base station, to a V2X
transmission UE out of cell coverage ((b) of FIG. 1) or to a V2X
transmission UE located in a different cell ((d) of FIG. 1). [0137]
V2X reception UE transmits information on transmission power of a
signal for path loss estimation to a V2X transmission UE via a
sidelink control channel [0138] A V2X reception UE may transmit
information on transmission power of a signal for path loss
estimation to a V2X transmission UE via a sidelink control channel.
In this case, the V2X reception UE may re-transmit the information
on the transmission power received from a base station to the V2X
transmission UE, or may transmit transmission power information
determined (or pre-configured) by the V2X reception UE itself to
the V2X transmission UE via the sidelink control channel without
the information on the transmission power received from the base
station. In this case, the V2X transmission UE may be located in
the same base station (or RSU) as the V2X reception UE, may be
located in a different base station from the V2X reception UE, or
may exist out of coverage of the base station. [0139] V2X reception
UE transmits information on transmission power of a signal for path
loss estimation to a V2X transmission UE via a sidelink data
channel [0140] A V2X reception UE may transmit information on
transmission power of a signal for path loss estimation to a V2X
transmission UE through a MAC CE transmitted via a sidelink data
channel. The V2X reception UE may re-transmit the information on
the transmission power received from a base station, or may
transmit transmission power information determined (or
pre-configured) by the V2X reception UE itself to the V2X
transmission UE via the sidelink data channel without the
information on the transmission power received from the base
station. In this case, the V2X transmission UE may be located in
the same base station as the V2X reception UE, may be located in a
different base station from the V2X reception UE, or may exist out
of coverage of the base station.
[0141] The V2X reception UE may transmit the information on the
transmission power of the signal for path loss estimation to the
V2X transmission UE through at least one of the above embodiments.
In this case, there may be various methods of configuring
transmission power information of the signal for path loss
estimation. When the V2X reception UE transmits the information on
the transmission power of the signal for path loss estimation to
the V2X transmission UE, the V2X reception UE may configure
transmission power information of the signal for path loss
estimation through at least one of the following embodiments.
[0142] A method of configuring the information on the transmission
power of the signal for path loss estimation according to an
embodiment will be described below. [0143] Information on
transmission power is directly transmitted [0144] Transmission
power of a signal for path loss estimation may be transmitted
through [x] bits. For example, the transmission power of the signal
for path loss estimation may be displayed in a range from -60 dBm
to 50 dBm by a 1 dBm. Accordingly, in the above example,
information on the transmission power of the signal for path loss
estimation may be transmitted through 7 bits. A method of
configuring the information on the transmission power of the signal
for path loss estimation may vary according to locations or
environments of the V2X transmission UE and the V2X reception UE as
follows. [0145] When the V2X transmission UE and the V2X reception
UE exist in coverage of the same base station, the V2X transmission
UE and the V2X reception UE may receive [x] bits that is a
transmission power value of a reference signal through system
information or RRC signaling from the same base station. When
transmission power information is transmitted to the V2X
transmission UE through system information or common RRC signaling,
the V2X reception UE may not transmit the information on the
transmission power of the signal for path loss estimation to the
V2X transmission UE. [0146] When the V2X reception UE and the V2X
transmission UE exist in coverages of different base stations or
when the V2X reception UE exists in coverage of the base station
and the V2X transmission UE exists out of the coverage of the base
station, the V2X reception UE may transmit transmission power
information of the signal for path loss estimation including [x]
bits to the V2X transmission UE via at least one of a sidelink
broadcast channel, a sidelink control channel, or a sidelink data
channel. [0147] The base station may transmit an explicit or
implicit command for transmission of the transmission power
information of the signal for path loss estimation including [x]
bits by the V2X reception UE via at least one of a sidelink
broadcast channel, a sidelink control channel, or a sidelink data
channel. In the case of the explicit command, the base station may
command through a 1-bit indication to transmit the transmission
power information of the signal for path loss estimation through
DCI or UE-specific RRC signaling transmitted to the V2X reception
UE. In the case of the implicit command, the base station may
command by differently configuring parameters for transmission of a
path loss signal in the V2X reception UE. For example, the base
station may differently configure a signal for path loss estimation
transmitted for path loss estimation with a V2X transmission UE out
of cell coverage and a signal for path loss estimation transmitted
for path loss estimation with a V2X transmission UE in the same
cell coverage (e.g., different sequence indexes, different
transmission resources, etc.). Also, the base station may
differently configure a signal for path loss estimation transmitted
for path loss estimation with a V2X transmission UE located in a
difference cell from a V2X reception UE and a signal for path loss
estimation transmitted for path loss estimation with a V2X
transmission UE located in the same cell (e.g., different sequence
indexes or index groups, different transmission resources, etc.).
[0148] Offset information for transmission power is transmitted
[0149] As in the above embodiment, when information on transmission
power is directly transmitted, full information on transmission
power of a signal for path loss estimation is notified, thereby
resulting in signaling overhead. In particular, when [x]-bit
information is transmitted via a sidelink broadcast channel or a
sidelink control channel, signaling overhead may increase. In order
to solve these problems, a method of determining a reference signal
and transmitting only offset information with respect to a
transmission power value of the reference signal may be considered.
In this case, the reference signal may be a synchronization signal
of a 5G or NR base station (gNB), a DMRS transmitted via a
broadcast channel (PBCH) of the gNB, or a CSI-RS of the 5G or NR
base station (gNB). In another example, the reference signal may be
a synchronization signal of a 4G or LTE base station (eNB), a DMRS
transmitted via a broadcast channel of the 4G or LTE base station
(eNB), or a CRS of the 4G or LTE base station (eNB). In another
example, the reference signal may be a sidelink synchronization
signal transmitted via a sidelink or a DMRS transmitted via a
sidelink broadcast channel. In another example, the reference
signal may be a DMRS transmitted via a sidelink control channel.
[0150] When a reference signal is a synchronization signal of a 5G
or NR base station (gNB), a DMRS transmitted via a broadcast
channel (PBCH) of the 5G or NR base station (gNB), or a CSI-RS of
the gNB, an operation may vary according to locations and
environments of the V2X transmission UE and the V2X reception UE as
follows. [0151] When the V2X transmission UE and the V2X reception
UE exist in coverage of the same base station, the V2X transmission
UE and the V2X reception UE may receive a transmission power value
of a reference signal through system information or RRC signaling
from the same base station. In this case, the system information
and the common RRC signaling may be signaling for supporting
general cellular communication, instead of for V2X. Offset
information may be transmitted through V2X dedicated system
information or common RRC signaling for supporting V2X. When the
offset information is transmitted to the V2X transmission UE
through the V2X dedicated system information or the RRC signaling
for supporting V2X, the V2X reception UE may not separately
transmit information on transmission power of a signal for path
loss estimation to the V2X transmission UE. [0152] When the V2X
reception UE and the V2X transmission UE exist in coverages of
different base stations or when the V2X reception UE exists in
coverage of the base station and the V2X transmission UE exists out
of the coverage of the base station, the V2X reception UE may
transmit an offset value to the V2X transmission UE via at least
one of a sidelink broadcast channel, a sidelink control channel, or
a sidelink data channel. [0153] The base station may transmit an
explicit or implicit command for transmission of offset information
for transmission power of a signal for path loss estimation by the
V2X reception UE, via at least one of a sidelink broadcast channel,
a sidelink control channel, or a sidelink data channel. In the case
of the explicit command, the base station may command through a
1-bit indication to transmit the offset information for the
transmission power of the signal for path loss estimation, through
DCI or UE-specific signaling transmitted to the V2X reception UE.
In the case of the implicit command, the base station may command
by differently configuring parameters for transmission of a path
loss signal in the V2X reception UE. For example, the base station
may differently configure a signal for path loss estimation
transmitted to a V2X transmission UE existing out of cell coverage
and a signal for path loss estimation transmitted to a V2X
transmission UE in the same cell coverage (e.g., different sequence
indexes, different transmission resources, etc.). Also, the base
station may differently configure a signal for path loss estimation
transmitted to a V2X transmission UE located in a different cell
from a V2X reception UE and a signal for path loss estimation
transmitted to a V2X transmission UE located in the same cell
(e.g., different sequence indexes, different transmission
resources, etc.). Through the configuration, the V2X reception UE
may determine whether to transmit transmission power information of
the signal for path loss estimation to the V2X transmission UE.
[0154] Likewise, when a reference signal is a synchronization
signal of an eNB, a DMRS transmitted via a broadcast channel (PBCH)
of the eNB, or a CRS of the eNB, an operation may vary according to
locations and environments of the V2X transmission UE and the V2X
reception UE as follows. [0155] When the V2X transmission UE and
the V2X reception UE exist in coverage of the same base station,
the V2X transmission UE and the V2X reception UE may receive a
transmission power value of a reference signal through system
information or RRC signaling from the eNB. In this case, the system
information and the common RRC signaling may be signaling for
supporting general 4G cellular communication (including LTE-NR dual
connectivity), instead of for V2X. Offset information may be
transmitted through V2X dedicated system information or common RRC
signaling for supporting V2X. When the offset information is
directly transmitted to the V2X transmission UE through the V2X
dedicated system information or the RRC signaling, the V2X
reception UE may not transmit information on transmission power of
a signal for path loss estimation to the V2X transmission UE.
[0156] When the V2X reception UE and the V2X transmission UE exist
in coverages of different base stations or when the V2X reception
UE exists in coverage of the base station and the V2X transmission
UE exists out of the coverage of the base station, the V2X
reception UE may transmit an offset value for transmission power of
a path loss estimation signal to the V2X transmission UE via at
least one of a sidelink broadcast channel, a sidelink control
channel, or a sidelink data channel. [0157] The base station may
transmit an explicit or implicit command for transmission of an
offset value for the transmission power of the signal for path loss
estimation by the V2X reception UE, via at least one of a sidelink
broadcast channel, a sidelink control channel, or a sidelink data
channel. In the case of the explicit command, the base station may
command through a 1-bit indication to transmit offset information
for the transmission power of the signal for path loss estimation,
through DCI or UE-specific RRC signaling transmitted to the V2X
reception UE. In the case of the implicit command, the base station
may command by differently configuring parameters for transmission
of a path loss signal in the V2X reception UE. For example, the
base station may differently configure a signal for path loss
estimation transmitted to a V2X transmission UE out of cell
coverage and a signal for path loss estimation transmitted to a V2X
transmission UE in the same cell coverage (e.g., different sequence
indexes, different transmission resources, etc.). Also, the base
station may differently configure a signal for path loss estimation
transmitted to a V2X transmission UE located in a different cell
from a V2X reception UE and a signal for path loss estimation
transmitted to a V2X transmission UE located in the same cell
(e.g., different sequence indexes, different transmission
resources, etc.). [0158] Because there may be various references
signals, information on which reference signal is to be used (e.g.,
a type of a reference signal to be used) may be required. This
information may be transmitted along with a transmission power
value of the reference signal or may be transmitted along with
offset information.
[0159] As described above, the base station or the V2X reception UE
may transmit a signal for path loss estimation and transmission
power information of the signal for path loss estimation to the V2X
transmission UE. The V2X transmission UE receiving the same may
estimate a path loss value of a sidelink by using [Equation 1]. The
V2X transmission UE may configure a transmission power value of a
physical channel (e.g., a sidelink control channel and a sidelink
data channel) via which sidelink control information and data
information are transmitted based on the estimated path loss value.
The V2X transmission UE may transmit the sidelink control
information and data information to the V2X reception UE based on
the configured transmission power value.
[0160] The above embodiments may be similarly or identically
applied to a groupcast communication method. For example, in a
groupcast communication method, there may exist a group header
functioning as a base station managing communication in a group.
Because group headers function as base stations, V2X UEs may obtain
a path loss value and may configure a transmission power value
based on the path loss value.
[0161] FIG. 7 is a diagram for describing a method of transmitting
and receiving a path loss measurement signal to estimate a sidelink
path loss, according to another disclosed embodiment.
[0162] FIG. 7 may correspond to a detailed embodiment of (b) of
FIG. 4. V2X UEs in coverage of a base station may perform downlink
synchronization and may obtain system information. In this case,
the downlink synchronization may be performed through a primary
synchronization signal/secondary synchronization signal (PSS/SSS)
received from the base station, or may be performed through a
synchronization signal received from a global navigation satellite
system (GNSS). The V2X UEs performing the downlink synchronization
may obtain system information related to V2X through a V2X
dedicated system information block (SIB) transmitted by the base
station gNB/RSU. Also, the V2X UEs in the coverage may perform
uplink synchronization through a random access procedure with the
base station and may perform an RRC connection procedure. In this
case, the uplink synchronization and the RRC connection procedure
may be performed by only one of a transmission UE or a reception
UE, or may be performed by both the transmission UE and the
reception UE.
[0163] Information on which UE from among the transmission UE and
the reception UE is to perform the uplink synchronization and the
RRC connection procedure may vary according to a transmission mode
of sidelink control information/data information, a sidelink path
loss estimation procedure, a signaling method, etc. For example, as
shown in FIG. 6, in a mode in which the base station transmits a
command for transmission of a path loss signal to a V2X reception
UE, the reception UE may have to perform the uplink synchronization
and the RRC connection procedure with the base station. Also, as
shown in FIG. 7, in a mode in which the base station transmits a
command for transmission of a path loss signal to a V2X
transmission UE, the transmission UE may have to perform the uplink
synchronization and the RRC connection procedure with the base
station.
[0164] Although not shown in FIGS. 6 and 7, when the base station
transmits a command for transmission of a path loss signal to the
V2X reception UE and transmits a command for reception of a path
loss signal to the V2X transmission UE, both the reception UE and
the transmission UE may have to perform the uplink synchronization
and the RRC connection procedure with the base station according to
a signaling method. For example, when a command of the base station
is transmitted to the V2X transmission UE and the V2X reception UE
through downlink control information (DCI), a MAC CE, or a UE
dedicated RRC message, the V2X transmission UE and the V2X
reception UE may perform the uplink synchronization and the RRC
connection procedure with the base station. When a command of the
base station is transmitted to the V2X transmission UE and the V2X
reception UE through V2X system information, the V2X transmission
UE and the V2X reception UE may not perform the uplink
synchronization and the RRC connection procedure with the base
station.
[0165] In FIG. 7, a reception UE may refer to a UE that receives
sidelink control information and data information, and a
transmission UE may refer to a UE that transmits sidelink control
information and data information. Accordingly, the reception UE and
the transmission UE in FIG. 7 may not be related to transmission
and reception of a path loss signal.
[0166] A V2X transmission UE or a V2X reception UE performing
downlink synchronization or uplink synchronization and RRC
connection configuration with the base station may perform sidelink
configuration for unicast communication. Such unicast link
configuration may be performed in a higher layer (e.g., an
application layer), and as shown in FIG. 7, the unicast link
configuration may be performed between the V2X transmission UE that
is to transmit V2X control information/data information in a
unicast method and the V2X reception UE that is to receive the V2X
control information/data information in the unicast method. Also,
although not shown in FIG. 7, the base station may engage in the
unicast link configuration. For example, the V2X transmission UE
may transmit a request for the unicast link configuration to the
base station, and the base station may transmit a response to the
unicast link configuration to the V2X reception UE. Also, the base
station may transmit a confirmation for the unicast link
configuration to the V2X transmission UE and the V2X reception UE.
However, as described above, because this procedure may be
performed in the higher layer, the procedure may not be identified
in a physical layer and a MAC layer.
[0167] As shown in FIG. 7, the base station may transmit a command
for a transmission request of a signal for path loss estimation to
the V2X transmission UE. In this case, the command of the base
station may be transmitted to the V2X transmission UE through
UE-specific DCI (or group common DCI) for a sidelink or through a
MAC CE or a UE-specific RRC message. When the command is
transmitted to the V2X transmission UE through the UE-specific DCI
or the group common DCI, the DCI may use a radio network temporary
identifier (RNTI) different from UE-specific DCI or group common
DCI used in existing cellular communication for distinguishment
from existing cellular communication.
[0168] Also, a command transmitted by the base station to the V2X
reception UE in FIG. 6 and a command transmitted by the base
station to the V2X transmission UE in FIG. 7 may be transmitted
through different UE-specific DCI (or group common DCI), MAC CEs,
or UE-specific RRC. In this case, the different UE-specific DCI (or
group common DCI) may be different DCI formats. Also, the different
MAC CEs may refer to different MAC CE formats. The V2X transmission
UE receiving the command from the base station may transmit a
request for transmission of a signal for path loss estimation to
the V2X reception UE. The V2X reception UE receiving the request
may transmit the signal for path loss estimation to the V2X
transmission UE. In this case, the request for transmission of the
signal for path loss estimation may be explicitly or implicitly
performed. In the case of the explicit request, the V2X
transmission UE may use a bit field for requesting to transmit the
signal for path loss estimation in sidelink control information
(SCI) transmitted via a sidelink control channel. The implicit
request may be performed when the V2X reception UE receives a
specific signal from the V2X transmission UE. For example, the V2X
transmission UE may transmit a sidelink synchronization signal, and
the V2X reception UE receiving the sidelink synchronization signal
may transmit the signal for path loss estimation to the V2X
transmission UE.
[0169] Also, unlike in FIG. 7, the V2X transmission UE may transmit
a request for transmission of the signal for path loss estimation
to the V2X reception UE after unicast link configuration without
the command of the base station. For example, the V2X transmission
UE may start a timer from a point of time when a request for
unicast link configuration is received or from a point of time when
the unicast link configuration succeeds, and may transmit the
request of the signal for path loss estimation to the V2X reception
UE at a point of time when the timer expires. Likewise, the V2X
reception UE may start a timer from a point of time when a request
for unicast link configuration is transmitted or from a point of
time when the unicast link configuration succeeds, and may expect
to receive the request for transmission of the signal for path loss
estimation from the V2X transmission UE at a point of time when the
timer expires. In another example, the V2X transmission UE may
transmit the request for transmission of the signal for path loss
estimation to the V2X reception UE after a certain period of time
(e.g., [x] subframes, [x] slots, or [x] ms) from a point of time
when unicast link configuration succeeds. Likewise, the V2X
reception UE may expect to receive the request for transmission of
the signal for path loss estimation after a certain period of time
(e.g., [x] subframes, [x] slots, or [x] ms) from a point of time
when unicast link configuration succeeds.
[0170] In another example where the V2X transmission UE transmits
the request for transmission of the signal for path loss estimation
to the V2X reception UE without the command of the base station,
when an RSRP value measured by the V2X transmission UE with the
base station is equal to or greater than (or greater than) a
specific threshold value configured by the base station or is equal
to or less than (or less than) a specific threshold value, the V2X
transmission UE may transmit the request for transmission of the
signal for path loss estimation to the V2X reception UE. In this
case, the base station may configure the RSRP threshold value in
the V2X transmission UE through a system transmission block for V2X
(V2X SIB) or a UE-specific RRC/common RRC message for V2X. In
another example, when a variation of the RSRP value with the base
station is equal to or greater than (or greater than) a specific
threshold value configured by the base station, the V2X
transmission UE may transmit the request for transmission of the
signal for path loss estimation to the V2X reception UE. Although
the V2X transmission UE satisfies a condition for the RSRP
threshold value configured by the base station, when the base
station sends a command for stopping transmitting the request for
transmission of the signal for path loss estimation, the V2X
transmission UE may stop transmitting the request for transmission
of the signal for path loss estimation.
[0171] In another example where the V2X transmission UE transmits
the request for transmission of the signal for path loss estimation
to the V2X reception UE without the command of the base station,
when a modulation order of V2X data information to be transmitted
by the V2X transmission UE is equal to or greater than, or greater
than a certain level, the V2X transmission UE may transmit the
request for transmission of the signal for path loss estimation to
the V2X reception UE. For example, when the modulation order of the
V2X data information to be transmitted by the V2X transmission UE
is equal to or greater than 64-QAM (or is 256-QAM greater than
64-QAM), the V2X transmission UE may transmit the request for
transmission of the signal for path loss estimation to the V2X
reception UE. In another example, when a transport block (TBS) size
of the V2X data information to be transmitted by the V2X
transmission UE is equal to or greater than, or greater than
specific bits, the V2X transmission UE may transmit the request for
transmission of the signal for path loss estimation to the V2X
reception UE. For example, when the TBS size of the V2X data
information to be transmitted is equal to or greater than (or
greater than) y bits, the V2X transmission UE may transmit the
request for transmission of the signal for path loss estimation to
the V2X reception UE. In another example, when an aggregation level
of V2X control information to be transmitted by the V2X
transmission UE is equal to or less than, or less than a certain
level, the V2X transmission UE may transmit the request for
transmission of the signal for path loss estimation to the V2X
reception UE (e.g., when the aggregation level is equal to or less
than 8, or is equal to 4 that is less than 8).
[0172] In another example where the V2X transmission UE transmits
the signal for path loss estimation to the V2X reception UE without
the command of the base station, when an RSRP value of a sidelink
channel previously measured by the V2X transmission UE is equal to
or greater than (or greater than) a specific threshold value
configured by the base station, or is equal to or less than (or
less than) a specific threshold value, the V2X transmission UE may
transmit the signal for path loss estimation to the V2X reception
UE. In this case, the base station may configure the RSRP threshold
value of the sidelink channel in the V2X transmission UE through a
system transmission block for V2X (V2X SIB) or UE-specific
RRC/common RRC message for V2X. In this case, when the RSRP value
of the sidelink channel satisfies a specific threshold value
condition configured by the base station at least once, the V2X
transmission UE may transmit the signal for path loss estimation to
the V2X reception UE. Alternatively, when the RSRP value of the
sidelink channel satisfies the specific threshold value condition
configured by the base station X times (or more), the V2X
transmission UE may transmit the signal for path loss estimation to
the V2X reception UE. In this case, X may be pre-defined, or may be
configured by the base station. In another example, when a
variation of the RSRP value of the sidelink channel is equal to or
greater than (or greater than) a specific threshold value
configured by the base station, the V2X transmission UE may
transmit the signal for path loss estimation to the V2X reception
UE. Even when the V2X transmission UE satisfies a condition for the
RSRP threshold value of the sidelink channel, which is configured
by the base station, when the base station transmits a command for
stopping transmitting the signal for path loss estimation, the V2X
transmission UE may stop transmitting the signal for path loss
estimation. In another example, a threshold value for the RSRP
value of the sidelink channel or the variation of the RSRP value of
the sidelink channel may be pre-configured without signaling from
the base station.
[0173] As shown in FIG. 7, the V2X reception UE receiving the
request for transmission of the signal for path loss estimation
from the V2X transmission UE may transmit the signal for path loss
estimation to the V2X transmission UE. In this case, the V2X
transmission UE may receive information on transmission power of
the signal for path loss estimation from the base station or the
V2X reception UE. A method of transmitting the information on the
transmission power of the signal for path loss estimation may be
performed in various ways as described with reference to FIG. 6.
Also, a method of configuring transmission power information of the
signal for path loss estimation may be performed by using one of
various examples described with reference to FIG. 6. The V2X
transmission UE receiving the signal for path loss estimation and
the transmission power information of the signal for path loss
estimation from the base station or the V2X reception UE may
estimate a path loss value of a sidelink by using [Equation 1]. The
V2X transmission UE may configure a transmission power value of a
physical channel (e.g., a sidelink control channel and a sidelink
data channel) via which sidelink control information and data
information are transmitted based on the estimated path loss value.
The V2X transmission UE may transmit the sidelink control
information and data information to the V2X reception UE based on
the configured transmission power value.
[0174] The above examples may be similarly or identically applied
to a groupcast communication method. For example, in a groupcast
communication method, there may exist a group header functioning as
a base station managing communication in a group. Because group
headers function as base stations, V2X UEs may obtain a path loss
value and may configure a transmission power value based on the
path loss value.
[0175] In FIG. 7, there may be a time relationship between a point
of time when the V2X reception UE receives the request for
transmission of the signal for path loss estimation transmitted by
the V2X transmission UE and a point of time when the V2X reception
UE transmits the signal for path loss estimation to the V2X
transmission UE in response to the request. For example, the V2X
transmission UE may include timing information on timing when the
signal for path loss estimation is to be transmitted by the V2X
reception UE, in request information transmitted by the V2X
transmission UE. That is, the V2X transmission UE may transmit
timing-related information in a bit field of sidelink control
information requesting the signal for path loss estimation, by
using [z] bits. In this case, a unit representing the timing
information may be the number of symbols (z symbols), the number of
slots (z slots), or the number of subframes (z subframes).
Accordingly, the V2X reception UE receiving the timing information
may transmit the signal for path loss estimation after z symbols
(or z slots or z subframes) from a point of time when the bit field
is received. In another example, the timing information may be
fixed, and the V2X transmission UE and the V2X reception UE may use
a pre-agreed value. In another example, when the V2X transmission
UE and the V2X reception UE are located in the same base station,
the base station may configure the timing information. In another
example, the V2X transmission UE may transmit the timing
information configured by the base station via a sidelink control
channel, to a V2X reception UE existing out of coverage of the base
station or to a V2X reception UE existing in a different base
station.
[0176] Until an estimated sidelink path loss value in FIGS. 6 and 7
is reflected in transmission of actual sidelink control information
and data information, there are pieces of information to be
transmitted and received between the V2X reception UE and the V2X
transmission UE. To transmit the pieces of information, it may be
necessary to consider how to configure a transmission power value.
For example, in FIG. 6, the V2X transmission UE may estimate a
sidelink path loss value by using a signal for path loss estimation
received from the V2X reception UE, and may configure a
transmission power value of sidelink control information and data
information based on the estimated sidelink path loss value. In
this case, it may be necessary to consider how to configure a
transmission power value of the signal for path loss estimation
transmitted by the V2X reception UE to the V2X transmission UE.
Also, in FIG. 7, the V2X transmission UE may transmit a request for
transmission of the signal for path loss estimation to the V2X
reception UE, and the V2X reception UE may transmit a signal for
sidelink path loss estimation to the V2X transmission UE based on
the request. In this case, it may be necessary to consider how to
configure transmission power values of the request for transmission
of the signal for path loss estimation transmitted by the V2X
transmission UE to the V2X reception UE and the signal for sidelink
path loss estimation transmitted by the V2X reception UE to the V2X
transmission UE. At least one of the following embodiments may be
used.
[0177] Pre-Defined Transmission Power Value is Used [0178] A base
station may configure a transmission power value through a V2X
dedicated SIB or RRC signaling. In this case, the configured
transmission power value may be a maximum transmission power value
of a UE (e.g., Pcmax), or an arbitrary value less than the maximum
transmission power value of the UE. In this case, the base station
may perform configuration by considering coverage of a sidelink and
interference of sidelink communication with an uplink of the base
station. The transmission power value may be used for all
transmissions until a sidelink path loss value is reflected in
transmission power value configuration of actual sidelink control
information and data information. [0179] In another example, a
transmission power value may be pre-configured without signaling
from the base station. The transmission power value may be used for
all transmissions until a sidelink path loss value is reflected in
transmission power value configuration of actual sidelink control
information and data information.
[0180] Transmission Power Value Reflecting a Sidelink Path Loss
Value Estimated by Itself is Used [0181] In FIG. 7, a V2X reception
UE may receive a request for transmission of a signal for path loss
estimation from a V2X transmission UE. When this procedure is used,
the V2X reception UE may measure sidelink RSRP and may estimate a
path loss value by using the request signal transmitted from the
V2X transmission UE. In this case, a transmission power value of
the request of the signal for path loss estimation, transmitted by
the V2X transmission UE, may be obtained by the V2X reception UE by
methods of Alt1. The V2X reception UE may configure a transmission
power value of the signal for path loss estimation transmitted to
the V2X transmission UE based on the path loss value estimated by
the V2X reception UE itself.
[0182] Transmission Power Value Reflecting a Downlink Path Loss
Value with a Base Station Estimated by Itself is Used [0183] When a
V2X reception UE exists in coverage of a base station, the V2X
reception UE may measure downlink RSRP and may estimate a downlink
path loss value by using an SSB or a CSI-RS of the base station.
The V2X reception UE may configure a transmission power value of a
signal for sidelink path loss estimation transmitted to a V2X
transmission UE based on the downlink path loss value. [0184] When
the V2X transmission UE exists in coverage of the base station, the
V2X transmission UE may estimate a downlink path loss value with
the base station (or RSU) by using an SSB or a CSI-RS of the base
station. The V2X transmission UE may configure a transmission power
value of transmission request information of a signal for sidelink
path loss estimation transmitted to the V2X reception UE, based on
the downlink path loss value with the base station. [0185] When
both the V2X reception UE and the V2X transmission UE exist in
coverage of the base station, the V2X reception UE may measure
downlink RSRP and may estimate a path loss value by using an SSB or
a CSI-RS of the base station. Also, the V2X transmission UE may
estimate a downlink path loss value with the base station (or RSU)
by using the SSB or the CSI-RS of the base station. In this case,
in FIG. 7, the V2X transmission UE may configure a transmission
power value of transmission request information of a signal for
sidelink path loss estimation transmitted to the V2X reception UE
based on the downlink path loss value estimated by the V2X
transmission UE itself. The V2X reception UE may configure a
transmission power value of the signal for sidelink path loss
estimation transmitted to the V2X transmission UE based on the
downlink path loss value with the base station.
[0186] FIG. 8A is a diagram for describing a method of transmitting
and receiving a path loss measurement signal to estimate an
inter-UE sidelink path loss, according to another disclosed
embodiment.
[0187] FIG. 8A may correspond to a detailed embodiment of (a) of
FIG. 5. V2X UEs in coverage of a base station may perform downlink
synchronization and may obtain system information. In this case,
the downlink synchronization may be performed through a primary
synchronization signal/secondary synchronization signal (PSS/SSS)
received from the base station, or may be performed through a
synchronization signal received from a global navigation satellite
system (GNSS). The V2X UEs performing the downlink synchronization
may obtain system information related to V2X through a V2X
dedicated system information block (SIB) transmitted by the base
station. Also, the V2X UEs in the coverage may perform uplink
synchronization through a random access procedure with the base
station and may perform an RRC connection procedure. In this case,
the uplink synchronization and the RRC connection procedure may be
performed by only one of a transmission UE or a reception UE, or
may be performed by both the transmission UE and the reception UE.
Information on which UE from among the transmission UE and the
reception UE is to perform the uplink synchronization and the RRC
connection procedure may vary according to a transmission mode of
sidelink control information/data information, a sidelink path loss
estimation procedure, and a signaling method. For example, as shown
in FIG. 8A, a mode in which the base station transmits a command
for transmission of a path loss signal to a V2X transmission UE,
the transmission UE may have to perform the uplink synchronization
and the RRC connection procedure with the base station. Also, as
shown in FIG. 9, in a mode in which the base station transmits a
command for transmission of a path loss signal to a V2X reception
UE, the reception UE may have to perform the uplink synchronization
and the RRC connection procedure with the base station. Although
not shown in FIGS. 8A and 9, when the base station transmits a
command for transmission of a path loss signal to the V2X
transmission UE and transmits a command for reception of a path
loss signal to the V2X reception UE, both the reception UE and the
transmission UE may have to perform the uplink synchronization and
the RRC connection procedure with the base station according to a
signaling method. For example, when a command of the base station
is transmitted to the V2X transmission UE and the V2X reception UE
through DCI, a MAC CE, or UE dedicated RRC, the V2X transmission UE
and the V2X reception UE may perform the uplink synchronization and
the RRC connection procedure with the base station. When a command
of the base station is transmitted to the V2X transmission UE and
the V2X reception UE through V2X system information, the V2X
transmission UE and the V2X reception UE may not perform the uplink
synchronization and the RRC connection procedure with the base
station.
[0188] The V2X transmission UE or reception UE performing the
uplink synchronization and the RRC connection configuration with
the base station may perform unicast link configuration. The
unicast link configuration may be performed in a higher layer
(e.g., an application layer), and as shown in FIG. 8A, the unicast
link configuration may be performed between the V2X transmission UE
that is to transmit V2X control information/data information in a
unicast method and the V2X reception UE that is to receive the V2X
control information/data information in the unicast method. Also,
although not shown in FIG. 8A, the base station may engage in the
unicast link configuration. For example, the V2X transmission UE
may transmit a request for the unicast link configuration to the
base station, and the base station may transmit a response to the
request to the V2X reception UE. Also, the base station may
transmit a confirmation for the unicast link configuration to the
V2X transmission UE and the V2X reception UE. However, as described
above, because this procedure may be performed in the higher layer,
the procedure may not be identified in a physical layer and a MAC
layer.
[0189] As shown in FIG. 8A, the base station may transmit a command
for transmission of a signal for path loss estimation to the V2X
transmission UE. In this case, the command of the base station may
be transmitted to the V2X transmission UE through UE-specific DCI
(or group common DCI) for a sidelink or through a MAC CE or
UE-specific RRC. When the command for transmission of the signal
for path loss estimation is transmitted to the V2X transmission UE
through UE-specific DCI or group common DCI, the DCI may use a
radio network temporary identifier (RNTI) different from
UE-specific DCI or group common DCI used in existing cellular
communication for distinguishment from existing cellular
communication.
[0190] Also, unlike in FIG. 8A, the V2X transmission UE may
transmit the signal for path loss estimation after unicast link
configuration without the command of the base station. For example,
the V2X transmission UE may start a timer from a point of time when
a request for unicast link configuration is received or from a
point of time when the unicast link configuration succeeds, and may
transmit the signal for path loss estimation at a point of time
when the timer expires. Likewise, the V2X reception UE may start a
timer from a point of time when a request for unicast link
configuration is transmitted or from a point of time when the
unicast link configuration succeeds, and may expect to receive the
signal for path loss estimation from the V2X transmission UE at a
point of time when the timer expires. In another example, the V2X
transmission UE may transmit the signal for path loss estimation
after a certain period of time (e.g., after [x] subframes, [x]
slots, or [x] ms) from a point of time when unicast link
configuration succeeds. Likewise, the V2X reception UE may receive
the signal for path loss estimation from the V2X transmission UE
after a certain period of time (e.g., [x] subframes, [x] slots, or
[x] ms) from a point of time when unicast link configuration
succeeds.
[0191] In another example where the V2X transmission UE transmits
the signal for path loss estimation without the command of the base
station, when an RSRP value measured by the V2X transmission UE
with the base station is equal to or greater than (or greater than)
a specific threshold value configured by the base station or is
equal to or less than (or less than) a specific threshold value,
the V2X transmission UE may transmit the signal for path loss
estimation to the V2X reception UE. In this case, the base station
may configure the RSRP value in the V2X transmission UE through a
system transmission block for V2X SIB (V2X SIB), or a UE-specific
RRC/common RRC message for V2X. In another example, when a
variation of the RSRP value with the base station is equal to or
greater than (or greater than) a specific threshold value
configured by the base station, the V2X transmission UE may
transmit the signal for path loss estimation to the V2X reception
UE. Although the V2X transmission UE satisfies a condition for the
RSRP value configured by the base station, when the base station
sends a command for stopping transmitting the signal for path loss
estimation, the V2X transmission UE may stop transmitting the
signal for path loss estimation.
[0192] In another example where the V2X transmission UE transmits
the signal for path loss estimation without the command of the base
station, when a modulation order of V2X data information to be
transmitted by the V2X transmission UE is equal to or greater than,
or greater than a certain level, the V2X transmission UE may
transmit the signal for path loss estimation. For example, when the
modulation order of the V2X data information to be transmitted by
the V2X transmission UE is equal to or greater than 64-QAM (or is
256-QAM greater than 64-QAM), the V2X transmission UE may transmit
the signal for path loss estimation to the V2X reception UE. In
another example, when an aggregation level of V2X control
information to be transmitted by the V2X transmission UE is equal
to or less than, or less than a certain level, the V2X transmission
UE may transmit the signal for path loss estimation (e.g., when the
aggregation level is equal to or less than 8, or is equal to 4 that
is less than 8). In another example, when a TBS size of the V2X
data information to be transmitted by the V2X transmission UE is
equal to or greater than (or greater than) a certain number of
bits, the V2X transmission UE may transmit the signal for path loss
estimation to the V2X reception UE. In another example, when there
are sidelink control information and data information to be
transmitted by the V2X transmission UE to the V2X reception UE, the
V2X transmission UE may always transmit the signal for path loss
estimation to the V2X reception UE along with the sidelink control
information and data information.
[0193] In another example where the V2X transmission UE transmits
the signal for path loss estimation to the V2X reception UE without
the command of the base station, when an RSRP value of a sidelink
channel previously measured by the V2X transmission UE is equal to
or greater than (or greater than) a specific threshold value
configured by the base station, or is equal to or less than (or
less than) a specific threshold value, the V2X transmission UE may
transmit the signal for path loss estimation to the V2X reception
UE. In this case, the base station may configure the RSRP threshold
value of the sidelink channel in the V2X transmission UE through a
system transmission block for V2X (V2X SIB), or a UE-specific
RRC/common RRC message for V2X. In this case, when the RSRP value
of the sidelink channel satisfies a specific threshold value
condition configured by the base station at least once, the V2X
transmission UE may transmit the signal for path loss estimation to
the V2X reception UE. Alternatively, when the RSRP value of the
sidelink channel satisfies the specific threshold value condition
configured by the base station X times (or more), the V2X
transmission UE may transmit the signal for path loss estimation to
the V2X reception UE. In this case, X may be pre-defined or may be
configured by the base station. In another example, when a
variation of the RSRP value of the sidelink channel is equal to or
greater than (or greater than) a specific threshold value
configured by the base station, the V2X transmission UE may
transmit the signal for path loss estimation to the V2X reception
UE. Even when the V2X transmission UE satisfies a condition for the
sidelink RSRP threshold value of the sidelink channel, which is
configured by the base station, when the base station transmits a
command for stopping transmitting the signal for path loss
estimation, the V2X transmission UE may stop transmitting the
signal for path loss estimation. In another example, a threshold
value of the RSRP value of the sidelink channel or the variation of
the RSRP value of the sidelink channel may be pre-configured
without signaling from the base station.
[0194] In the above examples where the V2X transmission UE
transmits the signal for path loss estimation, V2X transmission UEs
may refer to UEs having a capability to transmit a signal for V2X
path loss estimation. Accordingly, from among UEs having the
capability, V2X transmission UEs satisfying the above conditions
may transmit the signal for path loss estimation.
[0195] As shown in FIG. 8A, the base station may transmit a command
for transmission of the signal for path loss estimation to the V2X
transmission UE, and whether the V2X transmission UE is capable of
transmitting the signal for path loss estimation may be a V2X UE
capability (i.e., only UEs having a capability to transmit a signal
for V2X path loss estimation may transmit the signal for V2X path
loss estimation). In this case, the command of the base station may
be transmitted to the V2X transmission UE having the capability
through UE-specific DCI (or group common DCI) for a sidelink or
through a UE-specific RRC message. The V2X transmission UE
receiving the command for transmission of the signal for path loss
estimation may transmit the signal for path loss estimation to the
V2X reception UE. Alternatively, when the above condition is
satisfied (e.g., expiration of a timer, RSRP with the base station,
or a modulation order), the V2X transmission UE that is to transmit
the signal for path loss estimation may transmit the signal for
path loss estimation to the V2X reception UE. In this case, the V2X
reception UE may obtain information on transmission power of the
signal for path loss estimation by using one of the following
various methods.
[0196] A method of transmitting the information on the transmission
power of the signal for path loss estimation according to an
embodiment will be described below.
[0197] Base Station Transmits Information on Transmission Power of
a Signal for Path Loss Estimation to a V2X Reception UE Through RRC
Signaling [0198] A base station may transmit information on
transmission power of a signal for path loss estimation to a V2X
reception UE through RRC signaling. In detail, the base station may
transmit transmission power information of the signal for path loss
estimation to all V2X UEs in cell coverage through a V2X dedicated
system information block V2X SIB. In this case, the V2X reception
UE may receive the information even when there is no RRC connection
configuration with the base station. In another example, the base
station may transmit the information on the transmission power of
the signal for path loss estimation transmitted by a V2X
transmission UE to the V2X reception UE through UE dedicated RRC or
UE common RRC signaling. In this case, the V2X reception UE may
have to perform RRC connection configuration with the base station.
As described above, when the V2X reception UE directly receives the
information on the transmission power of the signal for path loss
estimation from the base station, the V2X transmission UE may not
transmit the information on the transmission power of the signal
for path loss estimation to the V2X reception UE.
[0199] V2X Transmission UE Transmits Information on Transmission
Power of a Signal for Path Loss Estimation to a V2X Reception UE
Via a Sidelink Broadcast Channel [0200] A V2X transmission UE may
transmit information on transmission power of a signal for path
loss estimation to a V2X reception UE via a sidelink broadcast
channel. In this case, the information on the transmission power
transmitted by the V2X transmission UE may be information received
from a base station. For example, as shown in (b) of FIG. 1, a
scenario in which the V2X transmission UE exists in coverage of the
base station and the V2X reception UE exists out of the coverage of
the base station may be considered. In this situation, the V2X
reception UE may not receive system information and RRC information
from the base station. Accordingly, the V2X transmission UE
existing in the coverage of the base station may transmit the
information on the transmission power of the signal for path loss
estimation via a sidelink broadcast channel so that the V2X
reception UE existing out of the coverage of the base station
estimates a sidelink path loss. [0201] In another example, as shown
in (d) of FIG. 1, the V2X reception UE and the V2X transmission UE
may exist in different cells. That is, a V2X reception UE UE-1 may
exist in coverage of a base station 1, and the V2X transmission UE
UE-2 may exist in coverage of a base station 2. In this case, the
V2X transmission UE UE-2 existing in the coverage of the base
station 2 may transmit the information on the transmission power of
the signal for path loss estimation to the V2X reception UE UE-1
existing in the coverage of the base station 1 via a sidelink
broadcast channel. [0202] The V2X transmission UE may transmit
transmission power information determined by the V2X transmission
UE itself via a sidelink broadcast channel, without the information
on the transmission power received from the base station, to a V2X
reception UE out of cell coverage ((b) of FIG. 1) or to a V2X
reception UE located in a different cell ((d) of FIG. 1).
[0203] V2X Transmission UE Transmits Information on Transmission
Power of a Signal for Path Loss Estimation to a V2X Reception UE
Via a Sidelink Control Channel [0204] A V2X transmission UE may
transmit information on transmission power of a signal for path
loss estimation to a V2X reception UE via a sidelink control
channel. In this case, the V2X transmission UE may re-transmit the
information on the transmission power received from a base station
to the V2X reception UE, or may transmit transmission power
information determined (or pre-configured) by the V2X transmission
UE itself to the V2X reception UE via the sidelink control channel
without the information on the transmission power received from the
base station. In this case, the V2X reception UE may be located in
the same base station (or RSU) as the V2X transmission UE, may be
located in a different base station from the V2X transmission UE,
or may exist out of coverage of the base station.
[0205] V2X Transmission UE Transmits Information on Transmission
Power of a Signal for Path Loss Estimation to a V2X Reception UE
Via a Sidelink Data Channel [0206] A V2X transmission UE may
transmit information on transmission power of a signal for path
loss estimation to a V2X reception UE through a MAC CE transmitted
via a sidelink data channel. The V2X transmission UE may
re-transmit the information on the transmission power received from
a base station, or may transmit transmission power information
determined (or pre-configured) by the V2X transmission UE itself to
the V2X transmission UE via the sidelink data channel without the
information on the transmission power received from the base
station. In this case, the V2X reception UE may be located in the
same base station (or RSU) as the V2X transmission UE, may be
located in a different base station from the V2X transmission UE,
or may exist out of coverage of the base station.
[0207] The V2X transmission UE may transmit the information on the
transmission power of the signal for path loss estimation to the
V2X reception UE through at least one of the above embodiments. In
this case, there may be various methods of configuring transmission
power information of the signal for path loss estimation. When the
V2X transmission UE transmits the information on the transmission
power of the signal for path loss estimation to the V2X reception
UE, the V2X transmission UE may configure transmission power
information of the signal for path loss estimation by using at
least one of the following embodiments.
[0208] A method of configuring the information on the transmission
power of the signal for path loss estimation according to an
embodiment will be described below.
[0209] Information on Transmission Power is Directly Transmitted
[0210] Transmission power of a signal for path loss estimation may
be transmitted through [x] bits. For example, transmission power of
the signal for path loss estimation may be displayed in a range
from -60 dBm to 50 dBm by 1 dBm. Accordingly, in the above example,
information on the transmission power of the signal for path loss
estimation may be transmitted through 7 bits. A method of
configuring the information on the transmission power of the signal
for path loss estimation may vary according to locations or
environments of the V2X transmission UE and the V2X reception UE as
follows. [0211] When the V2X transmission UE and the V2X reception
UE exist in coverage of the same base station, the V2X transmission
UE and the V2X reception UE may receive [x] bits that is a
transmission power value of a reference signal through system
information or RRC signaling from the same base station. When
transmission power information is transmitted to the V2X reception
UE through system information or common RRC signaling, the V2X
transmission UE may not transmit the information on the
transmission power of the signal for path loss estimation to the
V2X reception UE. [0212] When the V2X transmission UE and the V2X
reception UE exist in coverages of different base stations, or when
the V2X transmission UE may exist in coverage of the base station
and the V2X reception UE exists out of the coverage of the base
station, the V2X transmission UE may transmit transmission power
information of the signal for path loss estimation including [x]
bits to the V2X reception UE via at least one of a sidelink
broadcast channel, a sidelink control channel, or a sidelink data
channel. [0213] The base station may transmit an explicit or
implicit command for transmission of the transmission power
information of the signal for path loss estimation including [x]
bits by the V2X transmission UE via at least one of a sidelink
broadcast channel, a sidelink control channel, or a sidelink data
channel. In the case of the explicit command, the base station may
command through a 1-bit indication to transmit the transmission
power information of the signal for path loss estimation through
DCI or UE-specific RRC signaling transmitted to the V2X
transmission UE. In the case of the implicit command, the base
station may command by differently configuring parameters for
transmission of a path loss signal in the V2X transmission UE. For
example, the base station may differently configure a signal for
path loss estimation transmitted for path loss estimation with a
V2X reception UE out of cell coverage and a signal for path loss
estimation transmitted for path loss estimation with a V2X
reception UE in the same cell coverage (e.g., different sequence
indexes, different transmission resources, etc.). Also, the base
station may differently configure a signal for path loss estimation
transmitted for path loss estimation with a V2X reception UE
located in a different cell from a V2X transmission UE and a signal
for path loss estimation transmitted for path loss estimation with
a V2X reception UE located in the same cell (e.g., different
sequence indexes or index groups, different transmission resources,
etc.).
[0214] Offset Information for Transmission Power is Transmitted
[0215] As in the above embodiment, when information on transmission
power is directly transmitted, full information on transmission
power of a signal for path loss estimation is notified, thereby
resulting in signaling overhead. In particular, when [x]-bit
information is transmitted via a sidelink broadcast channel or a
sidelink control channel, signaling overhead may increase. In order
to solve these problems, a method of determining a reference signal
and transmitting only offset information with respect to a
transmission power value of the reference signal may be considered.
In this case, the reference signal may be a synchronization signal
of a 5G or NR base station (gNB), a DMRS transmitted via a
broadcast channel (PBCH) of the gNB, or a CSI-RS of the 5G or NR
base station (gNB). In another example, the reference signal may be
a synchronization signal of a 4G or LTE base station (eNB), a DMRS
transmitted via a broadcast channel of the 4G or LTE base station
(eNB), or a CRS of the 4G or LTE base station (eNB). In another
example, the reference signal may be a sidelink synchronization
signal transmitted via a sidelink or a DMRS transmitted via a
sidelink broadcast channel. In another example, the reference
signal may be a DMRS transmitted via a sidelink control channel.
[0216] When the reference signal is a synchronization signal of a
5G or NR base station (gNB), a DMRS transmitted via a broadcast
channel (PBCH) of the 5G or NR base station (gNB), or a CSI-RS of
the gNB, an operation may vary according to locations and
environments of the V2X transmission UE and the V2X reception UE as
follows. [0217] When the V2X transmission UE and the V2X reception
UE exist in coverage of the same base station, the V2X transmission
UE and the V2X reception UE may receive a transmission power value
of a reference signal through system information or RRC signaling
from the same base station. In this case, the system information
and the common RRC signaling may be signaling for supporting
general cellular communication, instead of for V2X. Offset
information may be transmitted through V2X dedicated system
information or common RRC signaling for supporting V2X. When the
offset information is transmitted to the V2X reception UE through
the V2X dedicated system information or the RRC signaling for
supporting V2X, the V2X transmission UE may not transmit
information on transmission power of a signal for path loss
estimation to the V2X reception UE. [0218] When the V2X reception
UE and the V2X transmission UE exist in coverages of different base
stations, or when the V2X reception UE exists in coverage of the
base station and the V2X transmission UE exists out of the coverage
of the base station, the V2X reception UE may transmit an offset
value to the V2X reception UE via at least one of a sidelink
broadcast channel, a sidelink control channel, and a sidelink data
channel. [0219] The base station may transmit an explicit or
implicit command for transmission of offset information for
transmission power of a signal for path loss estimation by the V2X
transmission UE, via at least one of a sidelink broadcast channel,
a sidelink control channel, or a sidelink data channel. In the case
of the explicit command, the base station may command through a
1-bit indication to transmit the offset information for the
transmission power of the signal for path loss estimation, through
DCI or UE-specific signaling transmitted to the V2X transmission
UE. In the case of the implicit command, the base station may
command by differently configuring parameters for transmission of a
path loss signal to the V2X transmission UE. For example, the base
station may differently configure a signal for path loss estimation
transmitted to a V2X reception UE existing out of cell coverage and
a signal for path loss estimation transmitted to a V2X reception UE
in the same cell coverage (e.g., different sequence indexes,
different transmission resources, etc.). Also, the base station may
differently configure a signal for path loss estimation transmitted
to a V2X reception UE located in a different cell from a V2X
transmission UE and a signal for path loss estimation transmitted
to a V2X reception UE located in the same cell (e.g., different
sequence indexes, different transmission resources, etc.). Through
the configuration, the V2X transmission UE may determine whether to
transmit transmission power information of the signal for path loss
estimation to the V2X reception UE. [0220] Likewise, when a
reference signal is a synchronization signal of an eNB, a DMRS
transmitted via a broadcast channel (PBCH) of the eNB, or a CRS of
the eNB, an operation may vary according to locations and
environments of the V2X transmission UE and the V2X reception UE as
follows. [0221] When the V2X transmission UE and the V2X reception
UE exist in coverage of the same base station, the V2X transmission
UE and the V2X reception UE may receive a transmission power value
of a reference signal through system information or RRC signaling
from the eNB. In this case, the system information and the common
RRC signaling may be signaling for supporting general 4G cellular
communication (including LTE-NR dual connectivity), instead of for
V2X. Offset information may be transmitted through V2X dedicated
system information or common RRC signaling for supporting V2X. When
the offset information is directly transmitted to the V2X
transmission UE through the V2X dedicated system information or the
RRC signaling, the V2X transmission UE may not transmit information
on transmission power of a signal for path loss estimation to the
V2X reception UE. [0222] When the V2X reception UE and the V2X
transmission UE exist in coverages of different base stations, or
when the V2X transmission UE exists in coverage of the base station
and the V2X reception UE exists out of the coverage of the base
station, the V2X transmission UE may transmit an offset value for
transmission power of a path loss estimation signal to the V2X
reception UE via at least one of a sidelink broadcast channel, a
sidelink control channel, or a sidelink data channel. [0223] The
base station may transmit an explicit or implicit command for
transmission of an offset value for the transmission power of the
signal for path loss estimation by the V2X transmission UE, via at
least one of a sidelink broadcast channel, a sidelink control
channel, or a sidelink data channel. In the case of the explicit
command, the base station may command through a 1-bit indication to
transmit offset information for the transmission power of the
signal for path loss estimation, through DCI or UE-specific RRC
signaling transmitted to the V2X transmission UE. In the case of
the implicit command, the base station may command by differently
configuring parameters for transmission of a path loss signal in
the V2X transmission UE. For example, the base station may
differently configure a signal for path loss estimation transmitted
to a V2X reception UE existing out of cell coverage and a signal
for path loss estimation transmitted to a V2X reception UE in the
same cell coverage (e.g., different sequence indexes, different
transmission resources, etc.). Also, the base station may
differently configure a signal for path loss estimation transmitted
to a V2X reception UE located in a different cell from a V2X
transmission UE and a signal for path loss estimation transmitted
to a V2X reception UE located in the same cell (e.g., different
sequence indexes, different transmission resources, etc.). Through
this configuration, the V2X transmission UE may determine whether
to transmit transmission power information of the signal for path
loss estimation to the V2X reception UE. [0224] Because there may
be various references signals, information on which reference
signal is to be used (e.g., a type of a reference signal to be
used) may be required. This information may be transmitted along
with a transmission power value of the reference signal or may be
transmitted along with offset information.
[0225] As described above, the base station or the V2X transmission
UE may transmit a signal for path loss estimation and transmission
power information of the signal for path loss estimation to the V2X
reception UE. The V2X reception UE receiving the same may estimate
a path loss value of a sidelink by using [Equation 1]. The V2X
reception UE may report an estimation result to the V2X
transmission UE. In this case, a reporting method may be performed
through one of the following various methods.
[0226] Referring to FIG. 8A, the V2X reception UE may report a path
loss estimation result to the V2X transmission UE, and in this
case, the V2X reception UE may report RSRP measured by the V2X
reception UE itself or may directly report a path loss value
estimated by the V2X reception UE itself.
[0227] A method of configuring reported information according to an
embodiment will be described below.
[0228] Measured RSRP Value is Reported [0229] A V2X reception UE
may report L1-RSRP or L3-RSRP measured by the V2X reception UE
itself to a V2X transmission UE. In this case, the L1-RSRP may
refer to layer 1 (PHY layer) RSRP, and the L3-RSRP may refer to
layer 3 RSRP. The L1-RSRP may refer to an instantaneous RSRP value
measured in a physical layer. In contrast, the L3-RSRP may refer to
an RSRP value obtained by layer 3 by averaging the L1-RSRP during a
certain period of time (e.g., 100 ms). In this case, a filter
coefficient for obtaining an average may be required. When the
L1-RSRP is averaged, the filter coefficient may be used to
determine a weight value between an RSRP value measured in the past
and an RSRP value measured in the present. Information on the
filter coefficient may use a filter coefficient value that is
configured from a base station or is pre-determined.
[0230] Estimated Path Loss Value is Reported [0231] A V2X reception
UE may directly report a path loss value estimated by the V2X
reception UE itself. To this end, the V2X reception UE may need to
obtain information on transmission power of a signal for path loss
estimation transmitted by a V2X transmission UE. This information
may be transmitted through various embodiments described with
reference to a method of transmitting the information on the
transmission power of the signal for path loss estimation or a
method of configuring the information on the transmission power of
the signal for path loss estimation.
[0232] Referring to FIG. 8A, the V2X reception UE may report RSRP
measured by the V2X reception UE itself or may report a path loss
value measured by the V2X reception UE itself to the V2X
transmission UE. In this case, a reported RSRP value or a path loss
value may be transmitted via the following channels.
[0233] A channel via which reported information is transmitted
according to an embodiment will be described below.
[0234] Transmission Via a Sidelink Feedback Channel (Physical
Sidelink Feedback Channel (PSFCH)) [0235] A V2X reception UE may
transmit an RSRP value measured by the V2X reception UE itself or a
path loss value estimated by the V2X reception UE itself to a V2X
transmission UE via a sidelink feedback channel. In this case, via
the feedback channel, only the RSRP or path loss value may be
transmitted, or the RSRP or path loss value may be multiplexed with
at least one of other pieces of sidelink feedback information and
may be transmitted. In this case, the sidelink feedback information
(SFI) may include hybrid automatic repeat request
(ARQ)-acknowledgement (HARQ-ACK), channel state information (CSI),
a rank indicator (RI), a precoder matrix indicator (PMI), a layer
indicator (LI), or a scheduling request (SR) of a sidelink
channel.
[0236] Transmission Via a Sidelink Data Channel (Physical Sidelink
Shared Channel (PSSCH)) [0237] An RSRP value measured by a V2X
reception UE or a path loss value estimated by the V2X reception UE
may be transmitted via a sidelink data channel. In this case, the
RSRP value or the estimated path loss value may be multiplexed with
sidelink data information and at least one of other pieces of
sidelink feedback information as described above transmitted via a
sidelink feedback channel and may be transmitted. Also, when the
V2X reception UE does not have data information to be transmitted
to a V2X transmission UE but is allocated the sidelink data channel
from a base station/RSU or another V2X UE, via the sidelink data
channel, only the RSRP value or the estimated path loss value may
be transmitted, or may be multiplexed with at least one of other
pieces of sidelink feedback information and may be transmitted.
[0238] In another example where the RSRP value or the estimated
path loss value is transmitted via the sidelink data channel, the
V2X reception UE may use a MAC control element (CE) transmitted via
the sidelink data channel.
[0239] When a specific V2X reception UE reports an RSRP value or a
path loss value by using the above channels, other V2X reception
UEs may also be performing reporting. Accordingly, in order to
prevent collision and interference between resources used by
different V2X reception UEs, it may be necessary to allocate and
control a resource in which reported information is transmitted. To
this end, there may be the following methods.
[0240] A resource in which reported information is transmitted
according to an embodiment will be described below.
[0241] Base Station Allocates a Resource for a Report [0242] When a
V2X reception UE and a V2X transmission UE exist in coverage of a
base station, the base station may allocate a time/frequency
resource in which the V2X reception UE is to transmit a report.
Also, the base station may allocate a time/frequency resource in
which the V2X transmission UE Is to receive a report. [0243] This
allocation information may be transmitted to the V2X reception UE
and the V2X transmission UE through a UE-dedicated RRC message or a
common RRC message. [0244] In another example, the base station may
allocate a resource to the V2X reception UE by using UE-specific
DCI for sidelink control information transmission, and may transmit
resource information to be received by the V2X transmission UE to
the V2X transmission UE by using UE-specific DCI for sidelink
control information reception. In this case, a format of the DCI
transmitted to the V2X transmission UE and a format of the DCI
transmitted to the V2X reception UE may be different from each
other. However, in this case, because DCI has to be transmitted to
each of a transmission UE and a reception UE, signaling overhead
may increase. In order to solve this problem, resource allocation
information may be simultaneously transmitted to the transmission
UE and the reception UE by using group common DCI. [0245] In
another example, there may be a relationship between a resource of
a signal for path loss estimation received by the V2X reception UE
and a resource in which the V2X reception UE is to report RSRP or a
path loss value. In this case, the V2X reception UE may be
pre-configured with a resource in which a signal for path loss
estimation is to be received from the base station. Accordingly,
the V2X reception UE may derive time/frequency/code resources that
may be used for the V2X reception UE to make a report to the V2X
transmission UE, by using time/frequency/code resources of the
signal for path loss estimation received by the V2X reception UE.
[0246] The V2X reception UE may exist in coverage of the base
station and the V2X transmission UE may exist out of the coverage
of the base station. In this case, although the base station may
allocate a time/frequency resource in which the V2X reception UE is
to transmit a report, the base station may not allocate a
time/frequency resource in which the V2X transmission UE is to
receive a report. In this case, there may be a separate resource
for V2X UEs existing out of the coverage of the base station. The
resource may be orthogonal to a resource that may be used by V2X
UEs existing in the coverage of the base station in
time/frequency/code domains. Accordingly, considering this, the
base station may allocate a resource in which the V2X reception UE
is able to transmit a report from among time/frequency resources in
which the V2X transmission UE is able to receive a report. [0247]
Allocation information of a resource in which the V2X reception UE
may make a report may be transmitted to the V2X reception UE and
the V2X transmission UE through a UE-dedicated RRC message or a
common RRC message. In another example, the base station may
allocate a resource by using UE-specific DCI for sidelink control
information transmission to the V2X reception UE. [0248] In another
example, there may be a relationship between a resource of a signal
for path loss estimation received by the V2X reception UE and a
resource in which the V2X reception UE is to report RSRP or a path
loss value. In this case, because the V2X transmission UE exists
out of the coverage of the base station, the V2X transmission UE
may be pre-configured with a resource in which the signal for path
loss estimation is to be transmitted. The V2X reception UE may be
configured from the base station with a resource in which the
signal for path loss estimation is to be received. Accordingly, the
V2X reception UE may derive time/frequency/code resources that may
be used for the V2X reception UE to make a report to the V2X
transmission UE, by using time/frequency/code resources of the
signal for path loss estimation received by the V2X reception UE
itself. [0249] The V2X reception UE may exist out of coverage of
the base station, and the V2X transmission UE may exist in the
coverage of the base station. In this case, although the base
station may allocate a time/frequency resource in which the V2X
transmission UE is to transmit a signal for path loss estimation,
the base station may not allocate a time/frequency resource in
which the V2X reception UE is to transmit a report. In this case,
there may be a separate resource for V2X UEs existing out of the
coverage of the base station. The resource may be orthogonal to a
resource that may be used by V2X UEs existing in the coverage of
the base station in time/frequency/code domains. Accordingly,
considering this, the base station may allocate time/frequency/code
resources in which the V2X transmission UE may transmit the signal
for path loss estimation. In this case, there may be a relationship
between a resource of the signal for path loss estimation
transmitted by the V2X transmission UE and a resource in which the
V2X reception UE is to report RSRP or a path loss value. [0250]
Allocation information of a resource in which the V2X transmission
UE may transmit the signal for path loss estimation may be
transmitted to the V2X transmission UE through a UE-dedicated RRC
message or a common RRC message. In another example, the base
station may allocate a resource for transmission of a signal for
sidelink path loss estimation by using UE-specific DCI to the V2X
transmission UE. The V2X reception UE may derive
time/frequency/code resources that may be used for the V2X
reception UE to make a report to the V2X transmission UE, by using
time/frequency/code resources of the signal for path loss
estimation received by the V2X reception UE itself. [0251] Both the
V2X reception UE and the V2X transmission UE may exist out of
coverage of the base station. In this case, the base station may
not allocate a time/frequency resource in which the V2X reception
UE is to transmit a report and a time/frequency resource in which
the V2X transmission UE is to receive a report. In this case, there
may be a separate resource for V2X UEs existing out of the coverage
of the base station. The resource may be orthogonal to a resource
that may be used by V2X UEs existing in the coverage of the base
station in time/frequency/code domains. [0252] There may be a
relationship between a resource of a signal for path loss
estimation received by the V2X reception UE and a resource in which
the V2X reception UE is to report RSRP or a path loss value.
Accordingly, the V2X reception UE may derive time/frequency code
resources that may be used for the V2X reception UE to make a
report to the V2X transmission UE, by using time/frequency/code
resources of the signal for path loss estimation received by the
V2X reception UE itself.
[0253] Another V2X UE Allocates a Resource for a Report [0254] A
V2X transmission UE may allocate a resource for a report of a V2X
reception UE. In this case, resource allocation information for a
report may be explicitly transmitted via a sidelink control
channel. Also, the resource allocation information may be
transmitted along with resource allocation information in which the
V2X reception UE receives a signal for path loss estimation. Also,
the V2X transmission UE may be configured with the resource
allocation information for the report of the V2X reception UE from
a base station, and may transmit the information received from the
base station to the V2X reception UE via the sidelink control
channel. In this case, the base station may transmit resource
candidates for the report to the V2X transmission UE, and the V2X
transmission UE may select one of the resource candidates
configured from the base station and may notify the selected one to
the V2X reception UE via the sidelink control channel. [0255] The
resource allocation information for the report may be implicitly
transmitted. In this case, there may be a relationship between a
resource of a signal for path loss estimation received by the V2X
reception UE and a resource in which the V2X reception UE is to
report RSRP or a path loss value. The V2X reception UE may be
configured with a resource in which the V2X reception UE is to
receive the signal for path loss estimation from the base station,
or may receive the information from the V2X transmission UE.
Accordingly, the V2X reception UE may derive time/frequency/code
resources that may be used for the V2X reception UE to make a
report to the V2X transmission UE, by using time/frequency/code
resources of the signal for path loss estimation received by the
V2X reception UE itself from the base station or the V2X
transmission UE.
[0256] When the V2X reception UE receives the signal for path loss
estimation from the V2X transmission UE and then reports a result
to the V2X transmission UE, the V2X reception UE may periodically
or aperiodically report the result. In an embodiment, periodic or
aperiodic reporting may have a relationship with an interval in
which the V2X reception UE is to perform reporting. For example, in
the case of the periodic reporting, a reception UE may continuously
perform reporting during a reporting interval, that is, between a
start time and an end time of reporting. Also, in the case of the
aperiodic reporting, the reception UE may perform reporting once at
a reporting time rather than configuring an interval during which
reporting is performed. Also, after the V2X reception UE receives
the signal for path loss estimation from the V2X transmission UE,
the V2X reception UE needs to determine a reporting timing
regarding when to perform reporting.
[0257] A reporting time according to an embodiment will be
described below.
[0258] Signaling is Received from a Base Station [0259] A base
station may notify a time interval in which reporting is to be
performed to a V2X reception UE and a V2X transmission UE through
RRC or MAC CE signaling. The V2X reception UE having received the
RRC or MAC CE signal may start reporting after a certain period of
time (e.g., after [x1] symbols, [x2] slots, or [x3] subframes from
a point of time when RRC signaling is received through a downlink
from the base station and HARQ-ACK is transmitted through an uplink
to the base station). Once the reporting starts, the V2X reception
UE may perform the reporting to the V2X transmission UE during an
interval configured by the base station. This operation may be
referred to as periodic reporting or semi-persistent reporting.
[0260] In another example, the base station may notify a point of
time in which reporting is to be performed to the V2X reception UE
and the V2X transmission UE through UE-specific DCI or group common
DCI. The V2X reception UE may transmit a report based on timing
information included in the received UE-specific DCI or group
common DCI. The V2X transmission UE may receive a report based on
timing information included in the received UE-specific DCI or
group common DCI. In another example, the V2X reception UE having
received the UE-specific DCI or group common DCI may transmit a
report to the V2X transmission UE after a fixed period of time
(e.g., after [x] ms or [x] slots). In this case, the fixed period
of time may be configured from the base station, or may be a
pre-agreed value between the V2X transmission UE and the V2X
reception UE. This operation may be referred to as aperiodic
reporting.
[0261] Signaling is Received from Another V2X UE [0262] A base
station may notify a time interval in which reporting is to be
performed to a V2X reception UE and a V2X transmission UE through
RRC or MAC CE signaling. The V2X transmission UE may indicate a
point of time at which the V2X reception UE is to perform reporting
to the V2X reception UE through sidelink control information. The
V2X reception UE may transmit a report based on timing information
included in the sidelink control information received by the V2X
reception UE. The V2X transmission UE may receive a report from the
V2X reception UE based on timing information included in the
sidelink control information transmitted by the V2X transmission
UE. This reporting may be performed during the time interval
received through the RRC or MAC CE signaling from the base station.
This operation may be referred to as periodic or semi-persistent
reporting. [0263] In another example, an operation may be performed
without information on a time interval in which reporting is to be
performed from the base station. In this case, the V2X reception UE
receiving sidelink control information from the V2X transmission UE
may perform reporting to the V2X transmission UE, based on timing
information and start information of a report (i.e., triggering
information of the report) included in the sidelink control
information. In another example, the V2X reception UE having
received the sidelink control information may transmit a report to
the V2X transmission UE after a fixed period of time (e.g., after
[x] ms or [x] slots). In this case, the fixed period of time may be
configured from the base station, or may be a pre-agreed value
between the V2X transmission UE and the V2X reception UE. This
operation may be referred to as aperiodic reporting. This operation
may be referred to as aperiodic reporting.
[0264] When the V2X reception UE receives a signal for path loss
estimation from the V2X transmission UE and then reports a result
to the V2X transmission UE, the V2X reception UE needs to determine
how to configure a transmission power value of a channel for
reporting.
[0265] Configuration of an initial transmission power value of a
channel in which reported information is transmitted according to
an embodiment will be described below.
[0266] Pre-Defined Transmission Power Value is Used [0267] A base
station may configure a transmission power value of a channel for
reporting in a V2X reception UE through a V2X dedicated SIB or RRC
signaling. In this case, the configured transmission power value
may be a maximum transmission power value of a UE (e.g., Pcmax), or
an arbitrary value less than the maximum transmission power value
of the UE. In this case, the base station may perform configuration
by considering coverage of a sidelink and interference of sidelink
communication with an uplink of the base station. [0268] In the
absence of the base station (i.e., when communication between V2X
UEs is performed out of coverage of the base station), a
transmission power value of a channel reported by the V2X reception
UE to the V2X transmission UE may be pre-configured. [0269]
Transmission power value reflecting a sidelink path loss value
estimated by itself is used [0270] As shown in FIG. 8A, a V2X
reception UE may measure RSRP through a signal for path loss
estimation received from a V2X transmission UE, and may estimate a
sidelink path loss value. In this case, the V2X reception UE may
configure a transmission power value of a channel reported to the
V2X transmission UE based on a sidelink path loss value estimated
by the V2X reception UE itself.
[0271] Transmission Power Value Reflecting a Downlink Path Loss
Value with a Base Station Estimated by Itself is Used [0272] When a
V2X reception UE exists in coverage of a base station, the V2X
reception UE may configure a transmission power value of a channel
reported to a V2X transmission UE based on RSRP measured by using
an SSB or a CSI-RS of the base station and a downlink path loss
value estimated by using the RSRP.
[0273] The V2X transmission UE may transmit sidelink control
information and data information to the V2X reception UE based on
an RSRP value or a path loss estimation value reported from the V2X
reception UE.
[0274] The above embodiments may be similarly or identically
applied to a groupcast communication method. For example, in a
groupcast communication method, there may exist a group header
functioning as a base station managing communication in a group.
Such group headers may function as base stations.
[0275] FIG. 8B is a diagram for describing in more detail a method
of estimating an inter-UE sidelink path loss according to an
embodiment of FIG. 8A.
[0276] In FIG. 8A, a transmission UE may transmit a signal for path
loss estimation to a reception UE, the reception UE receiving the
signal may measure RSRP by using a path loss estimation signal and
may report the RSRP to the transmission UE, and the transmission UE
may estimate a path loss value of a sidelink by using the received
RSRP. Also, the RSRP reported by the reception UE to the
transmission UE may be L1-RSRP or L3-RSRP. FIG. 8B illustrates a
specific example where the reception UE reports L1-RSRP to the
transmission UE.
[0277] In FIG. 8B, the same procedure as that in FIG. 8A will not
be described. For example, although not shown in FIG. 8B, downlink
synchronization with a base station and system parameter
acquisition, uplink synchronization and RRC connection
configuration, and unicast link configuration (PC-5 RRC connection
configuration) between the transmission UE and the reception UE may
be performed in the same manner as that in FIG. 8A. Also, the
transmission UE may receive a command for transmission of a
sidelink path loss estimation signal from the base station.
[0278] In order to estimate a path loss, an L3-RSRP value filtered
in layer 3 is required. In more detail, a physical layer (layer 1)
may calculate an L1-RSRP value and may transmit the L1-RSRP value
to layer 3, and the layer 3 may obtain the L3-RSRP value by
obtaining an average in a time domain, or a time domain and a
spatial domain by using the L1-RSRP value received from the
physical layer. For more accurate path loss estimation, an average
needs to be obtained during a sufficiently long time.
[0279] When the reception UE reports L1-RSRP to the transmission
UE, the above L3 filtering operation has to be performed during a
sufficiently long time for accurate path loss estimation. To this
end, the reception UE may have to report the L1-RSRP to the
transmission UE several times. Because the L1-RSRP is a value
calculated in the layer 1, the L1-RSRP may be transmitted via a
sidelink feedback channel (physical sidelink feedback channel
(PSFCH)) or a sidelink data channel (physical sidelink shared
channel (PSSCH)). Accordingly, when the reception UE has to report
the L1-RSRP to the transmission UE several times, it means that the
reception UE has to transmit the PSFCH or the PSSCH to the
transmission UE several times. Because a V2X UE may not be able to
simultaneously perform transmission and reception, the reception UE
may not be able to receive sidelink control information and data
information that may be transmitted from another transmission UE
while the reception UE transmits the PSFCH or the PSSCH several
times. Also, the V2X UE may not be able to simultaneously transmit
two or more different channels in one carrier (i.e., two or more
different channels may not be frequency-divided and transmitted in
one carrier). Accordingly, while the reception UE transmits the
PSFCH or the PSSCH to the transmission UE several times to report
the L1-RSRP, the reception UE may not be able to transmit sidelink
control information and data information to another UE. In order to
solve these problems, N L1-RSRP reports may be transmitted in the
time domain once through a MAC CE shown in (c) or (d) of FIG.
8D.
[0280] As another problem of a case where the reception UE reports
the L1-RSRP to the transmission UE, agreement related to
transmission and reception of the L1-RSRP may be required between
the transmission UE and the reception UE so that the transmission
UE receives the L1-RSRP transmitted by the reception UE and
performs L3 filtering. In more detail, as shown in FIG. 8B, after
the reception UE receives a sidelink path loss estimation signal
transmitted from the transmission UE and measures the L1-RSRP,
agreement as to when to report the L1-RSRP to the transmission UE
may be required. In other words, the transmission UE needs to know
a point of time when an L1-RSRP report is transmitted from the
reception UE after the sidelink path loss estimation signal is
transmitted.
[0281] For example, the transmission UE may expect that the L1-RSRP
is to be reported from the reception UE after [x1] ms or [x2]
slots, from a slot on which the sidelink path loss estimation
signal is transmitted. However, when there is no PSFCH or PSSCH
resource for reporting the L1-RSRP at a point of time when the
reception UE reports the L1-RSRP, or when serious congestion occurs
in spite of the existence of the PSFCH or PSSCH resource, the
reception UE may not be able to report the L1-RSRP to the
transmission UE. Accordingly, in order for the transmission UE to
perform L3 filtering by using the L1-RSRP reported from the
reception UE, a sufficiently long reception window time needs to be
secured. That is, when the transmission UE expects that the L1-RSRP
is to be reported from the reception UE every [Xl] ms or [x2] slots
after transmission of the sidelink path loss estimation signal, the
transmission UE may attempt to receive the L1-RSRP during +.DELTA.1
ms or -.DELTA.1 ms from [x1] ms, or may attempt to receive the
L1-RSRP during +.DELTA.2 ms or -.DELTA.2 ms from [x2] slots.
[0282] In another example, in order for the transmission UE to
perform L3 filtering, the transmission UE may have to perform
filtering during a total of [x4] ms or a total of [x3] L1-RSRP
values reported from the reception UE every [x1] ms or every [x2]
slots. Accordingly, the reception UE may have to continuously
perform transmission to the transmission UE, until the number of
L1-RSRP values reported every [x1] ms or [x2] slots is a total of
[x3] (the total number of L1-RSRP values reported by the reception
UE to the transmission UE is N in FIG. 8B). Alternatively, the
reception UE may have to continuously transmit, to the transmission
UE, the L1-RSRP reported every [x1] ms or [x2] slots up to a total
of [x4] ms.
[0283] In another example, although not shown in FIG. 8B, the
transmission UE may transmit a command for stopping reporting the
L1-RSRP to the reception UE. The reception UE may report the
L1-RSRP every [x1] ms or [x2] slots, until the reception UE
receives the command for stopping reporting the L1-RSRP from the
transmission UE. The command for stopping reporting the L1-RSRP may
be included in PC-5 RRC signaling, a MAC CE, or SCI
information.
[0284] In another example, an operation may be performed based on a
timer. In more detail, the transmission UE may transmit a sidelink
path loss estimation signal and may start a T1 timer. The
transmission UE may maintain a reception window for receiving an
L1-RSRP value reported from the reception UE until the T1 timer
expires. When the T1 timer expires, the transmission UE may derive
a layer-3 RSRP value by using an L1-RSRP report received until the
T1 timer expires. The reception UE may receive the sidelink path
loss estimation signal and may start a T2 timer. The reception UE
may transmit an L1-RSRP value to the transmission UE at least once
on an available resource until the T2 timer expires. When the T2
timer expires, the reception UE may stop transmitting the L1-RSRP
report. In the above example, T1 and T2 may be the same or
different from each other.
[0285] In the above example, when the transmission UE does not
receive any L1-RSRP report from the reception UE until the T1 timer
of the transmission UE expires, the transmission UE may transmit
information for notifying this (e.g., HARQ-NACK) to the reception
UE. The reception UE receiving the information may re-configure the
T2 timer that is previously running (i.e., reset the T2 timer that
is previously running) and may report the L1-RSRP to the
transmission UE. In another example, when the transmission UE
secures sufficient L1-RSRP samples for performing layer-3 filtering
before the T1 timer expires (i.e., when N RSRP values are secured),
the transmission UE may transmit information for notifying this
(e.g., transmission of HARQ-ACK) to the reception UE and may
terminate the T1 timer. When the reception UE receives the
information indicating that sufficient L1-RSRP samples are secured
from the transmission UE and the T2 timer of the reception UE does
not expire, the reception UE may terminate the T2 timer.
[0286] [x1], [x2], [x3], [x4], 41, 42, T1, T2 and filtering
coefficients for performing L3 filtering may be configured by the
base station through system information or RRC signaling. In
another example, the transmission UE and the reception UE may
perform PC-5 RRC connection configuration during unicast link
connection configuration, and in this case, through PC-5 RRC
signaling. In another example, the parameters may be fixed values,
which may refer to values embedded in the transmission UE and the
reception UE.
[0287] FIG. 8C is another diagram for describing in more detail a
method of estimating an inter-UE sidelink path loss according to an
embodiment of FIG. 8A.
[0288] In FIG. 8C, the same procedure as that in FIG. 8A will not
be described. For example, although not shown in FIG. 8C, downlink
synchronization with a base station and system parameter
acquisition, uplink synchronization and RRC connection
configuration, and unicast link configuration (PC-5 RRC connection
configuration) between a transmission UE and a reception UE may be
performed in the same manner as that in FIG. 8A. Also, the
transmission UE may receive a command for transmission of a
sidelink path loss estimation signal from the base station.
[0289] Unlike in FIG. 8B in which the reception UE reports L1-RSRP
to the transmission UE, in FIG. 8C, when the reception UE reports
L3-RSRP to the transmission UE, the reception UE may report RSRP to
the transmission UE only once. Accordingly, problems occurring when
the reception UE reports L1-RSRP to the transmission UE may be
solved. However, in the case of L3-RSRP reporting, because a final
value of reported RSRP is generated in layer 3, L3-RSRP has to be
reported from RRC of the reception UE and transmitted to RRC of the
transmission UE, and may be transmitted via a PSSCH.
[0290] Agreement may be required between the transmission UE and
the reception UE so that the transmission UE receives the L3-RSRP
transmitted by the reception UE and estimates a sidelink path loss
value. In more detail, as shown in FIG. 8C, after the reception UE
receives a sidelink path loss estimation signal transmitted from
the transmission UE and measures the L3-RSRP, agreement as to when
to report the L3-RSRP to the transmission UE may be required. In
other words, the transmission UE needs to know a point of time when
an L3-RSRP report is transmitted from the reception UE after the
sidelink path loss estimation signal is transmitted.
[0291] For example, the transmission UE may expect that the L3-RSRP
is to be reported from the reception UE after [x1] ms or [x2]
slots, from a slot on which the sidelink path loss estimation
signal is transmitted. However, when there is no PSSCH resource for
reporting the L3-RSRP at a point of time when the reception UE
reports the L3-RSRP or when serious congestion occurs in spite of
the existence of the PSSCH resource for reporting the L3-RSRP, the
reception UE may not be able to report the L3-RSRP to the
transmission UE. Accordingly, in order for the transmission UE to
estimate a sidelink path loss value by using the L3-RSRP reported
from the reception UE, a sufficiently long reception window time
needs to be secured. That is, when the transmission UE expects that
the L3-RSRP is to be reported from the reception UE every [x1] ms
or every [x2] slots after transmission of the sidelink path loss
estimation signal transmitted by the transmission UE itself, the
transmission UE may attempt to receive the L3-RSRP during +.DELTA.1
ms or -.DELTA.1 ms from [x1] ms, or may attempt to receive the
L3-RSRP during +.DELTA.2 ms or -.DELTA.2 ms from [x2] slots.
[0292] In another example, an operation may be performed based on a
timer. In more detail, the transmission UE may transmit a sidelink
path loss estimation signal and may start a T1 timer. The
transmission UE may main a reception window for receiving an
L3-RSRP value reported from the reception UE until the T1 timer
expires. The reception UE may receive the sidelink path loss
estimation signal and may start a T2 timer. The reception UE may
perform an operation for finding an available resource for
reporting the L3-RSRP value to the transmission UE (e.g., a sensing
and resource selection operation) until the T2 timer expires. The
reception UE not finding the available resource for reporting the
L3-RSRP until the T2 timer expires may stop reporting the L3-RSRP.
In the above example, T1 and T2 may be the same or different from
each other.
[0293] In another example, when the transmission UE does not
receive any L3-RSRP report from the reception UE until the T1 timer
expires, the transmission UE may give up receiving the L3-RSRP.
Alternatively, when the transmission UE does not receive the
L3-RSRP report from the reception UE until the T1 timer expires,
the transmission UE may transmit information indicating this (e.g.,
HARQ-NACK) to the reception UE. The reception UE receiving the
information may re-configure the T2 timer that is previously
running (i.e., reset the T2 timer that is previously running), and
may re-report the L3-RSRP to the transmission UE.
[0294] [x1], [x2] through .DELTA.1, .DELTA.2, T1, T2 and filtering
coefficients for performing L3 filtering may be configured by the
base station through system information or RRC signaling. In
another example, the transmission UE and the reception UE may
perform PC-5 RRC connection configuration during unicast link
connection configuration, and in this case, through PC-5 RRC
signaling. In another example, the parameters may be fixed values,
which may refer to values embedded in the transmission UE and the
reception UE.
[0295] FIG. 8D is a diagram for describing a MAC CE format for
reporting an inter-UE sidelink RSRP value.
[0296] In (a) of FIG. 8D, a MAC CE includes 8 bits, and RSRP
transmitted through the MAC CE is represented as 7 bits (first
1-bit is a reserved bit). In this case, the RSRP may be L1-RSRP.
The RSRP may have a range from -140 dBm to -44 dBm with 1 dB
size.
[0297] (b) of FIG. 8D is another example of a MAC CE for
transmitting RSRP. Unlike in (a) of FIG. 8D, in (b) of FIG. 8D, a
UE ID including N bits may be transmitted along with 7-bit RSRP. In
this case, the UE ID may include a source ID of a transmission UE,
a destination ID of a reception UE, or both a source ID and a
destination ID. When one of the source ID and the destination ID is
transmitted along with the RSRP through the MAC CE, the source ID
or the destination ID may include 16 bits or 24 bits. When both the
source ID and the destination ID are transmitted along with the
RSRP through the MAC CE, bit sizes of the source ID and the
destination ID may be each 16 bits or 24 bits, and may be the same
or different from each other. That is, when it is assumed that a
bit size of the source ID is N1 and a bit size of the destination
ID is N2, N1=N2 or N1.noteq.N2, and each of N1 and N2 may be 16
bits or 24 bits.
[0298] (c) of FIG. 8D is another example of a MAC CE for
transmitting RSRP. Unlike in (a) of FIG. 8D, N RSRP values are
transmitted through one MAC CE. That is, assuming that the
reception UE has to report N L1-RSRP values to the transmission UE
as in FIG. 8B, when the MAC CE of (a) of FIG. 8D) is used, N MAC CE
transmissions may be required. In this case, signaling overhead may
increase and half-duplexing may increase. Accordingly, it may be
preferable that the reception UE transmits N L1-RSRP values through
one MAC CE as shown in (c) or (d) of FIG. 8D.
[0299] (d) of FIG. 8D is another example of a MAC CE for
transmitting RSRP. Like in (c) of FIG. 8D, N RSRP values are
transmitted through one MAC CE. However, unlike in (c) of FIG. 8D,
a first RSRP value from among the N RSRP values may include 7 bits,
and the remaining N-1 RSRP values may each include 4 bits. In more
detail, each of the N RSRP values in (c) of FIG. 8D may include 7
bits, and may be represented in a range from -140 dBm to -44 dBm
with 1 dB size. Although a first RSRP value includes 7 bits in (d)
of FIG. 8D like in (c) of FIG. 8D, second to last N.sup.th RSRP
values may be RSRP values each representing a difference from a
previously reported RSRP value. For example, a second RSRP value
RSRP-2 included in the MAC CE and transmitted may refer to a
difference between a first RSRP value RSRP-1 that is firstly
reported and an RSRP value that is secondly measured. A third RSRP
value RSRP-3 included in the MAC CE and transmitted may refer to a
difference between the second RSRP value RSRP-2 that is secondly
reported and an RSRP value that is thirdly measured. Such an RSRP
value difference may include 4 bits as shown in (d) of FIG. 8D, and
may be represented in a range from -140 dBm to -44 dBm with 2 dB
size. A method of (d) of FIG. 8D may reduce the size of bits
transmitted through a MAC CE when compared to (c) of FIG. 8D. In
more detail, because 3N bits may be reduced, MAC CE overhead may be
significantly reduced as N increases (as the number of reported
L-RSRP values increases).
[0300] The reception UE may be configured with information on
whether to report L1-RSRP by using the MAC CE of (a) of FIG. 8D or
to report L1-RSRP by using the MAC CE of (c) and/or (d) of FIG. 8D.
It means that the transmission UE may be configured with
information on whether to receive L1-RSRP by using the MAC CE of
(a) of FIG. 8D or to receive L1-RSRP by using the MAC CE of (c)
and/or (d) of FIG. 8D. This configuration may be received through
system information or RRC signaling of a base station or may be
received through PC-5 RRC signaling. In another example, this
configuration may be pre-configured.
[0301] FIG. 9 is a diagram for describing a method of transmitting
and receiving a path loss measurement signal to estimate an
inter-UE sidelink path loss, according to another disclosed
embodiment.
[0302] FIG. 9 may correspond to a detailed embodiment of (b) of
FIG. 5. V2X UEs in coverage of a base station may perform downlink
synchronization and may obtain system information. In this case,
the downlink synchronization may be performed through a primary
synchronization signal/secondary synchronization signal (PSS/SSS)
received from the base station, or may be performed through a
synchronization signal received from a global navigation satellite
system (GNSS). The V2X UEs performing the downlink synchronization
may obtain system information related to V2X through a V2X
dedicated system information block (SIB) transmitted by the base
station gNB/RSU. Also, the V2X UEs in the coverage may perform
uplink synchronization through a random access procedure with the
base station and may perform an RRC connection procedure. In this
case, the uplink synchronization and the RRC connection procedure
may be performed by only one of a transmission UE or a reception
UE, or may be performed by both the transmission UE and the
reception UE.
[0303] Information on which UE from among the transmission UE and
the reception UE is to perform the uplink synchronization and the
RRC connection procedure may vary according to a transmission mode
of sidelink control information/data information, a sidelink path
loss estimation procedure, a signaling method, etc. For example, as
shown in FIG. 8A, in a mode in which the base station transmits a
command for transmission of a path loss signal to a V2X
transmission UE, the transmission UE may have to perform the uplink
synchronization and the RRC connection procedure with the base
station. Also, as shown in FIG. 9, in a mode in which the base
station transmits a command for transmission of a path loss signal
to a V2X reception UE, the reception UE may have to perform the
uplink synchronization and the RRC connection procedure with the
base station.
[0304] Although not shown in FIGS. 8A and 9, when the base station
transmits a command for transmission of a path loss signal to the
V2X reception UE and transmits a command for reception of a path
loss signal to the V2X transmission UE, both the reception UE and
the transmission UE may perform the uplink synchronization and the
RRC connection procedure with the base station according to a
signaling method. In FIG. 9, a reception UE may refer to a UE that
receives sidelink control information and data information, and a
transmission UE may refer to a UE that transmits sidelink control
information and data information. Accordingly, the reception UE and
the transmission UE in FIG. 9 may not be related to transmission
and reception of a path loss signal.
[0305] A V2X transmission UE or a V2X reception UE performing
uplink synchronization and RRC connection configuration with the
base station may perform unicast link configuration. This unicast
link configuration may be performed in a higher layer (e.g., an
application layer), and as shown in FIG. 9, the unicast link
configuration may be performed between the V2X transmission UE that
is to transmit V2X control information/data information in a
unicast method and the V2X reception UE that is to receive the V2X
control information/data information in the unicast method. Also,
although not shown in FIG. 8A, the base station may engage in the
unicast link configuration. For example, the V2X transmission UE
may transmit a request for the unicast link configuration to the
base station, and the base station may transmit a response to the
unicast link configuration to the V2X reception UE. Also, the base
station may transmit a confirmation for the unicast link
configuration to the V2X transmission UE and the V2X reception UE.
However, as described above, because this procedure may be
performed in the higher layer, the procedure may not be identified
in a physical layer and a MAC layer.
[0306] As shown in FIG. 9, the base station may transmit a command
for a transmission request of a signal for path loss estimation to
the V2X reception UE. In this case, the command of the base station
may be transmitted to the V2X reception UE through UE-specific DCI
(group common DCI) for a sidelink or through a MAC CE or a
UE-specific RRC message. When the command is transmitted to the V2X
reception UE through the UE-specific DCI or the group common DCI,
the DCI may use a radio network temporary identifier (RNTI)
different from UE-specific DCI or group common DCI used in existing
cellular communication for distinguishment from existing cellular
communication.
[0307] Also, unlike in FIG. 9, the V2X reception UE may transmit a
request for transmission of the signal for path loss estimation to
the V2X transmission UE after unicast link configuration without
the command of the base station. For example, the V2X reception UE
may start a timer from a point of time when a request for unicast
link configuration is received or from a point of time when the
unicast link configuration succeeds, and may transmit the request
for transmission of the signal for path loss estimation at a point
of time when the timer expires. Likewise, the V2X transmission UE
may start a timer from a point of time when a request for unicast
link configuration is transmitted or from a point of time when the
unicast link configuration succeeds, and may expect to receive the
request for transmission of the signal for path loss estimation
from the V2X reception UE at a point of time when the timer
expires. In another example, the V2X reception UE may transmit the
request for transmission of the signal for path loss estimation to
the V2X transmission UE after a certain period of time (e.g., after
[x] subframes, [x] slots, or [x] ms) from a point of time when
unicast link configuration succeeds. Likewise, the V2X transmission
UE may expect to receive the request for transmission of the signal
for path loss estimation from the V2X reception UE after a certain
period of time (e.g., [x] subframes, [x] slots, or [x] ms) from a
point of time when unicast link configuration succeeds.
[0308] In another example where the V2X reception UE transmits the
request of the signal for path loss estimation to the V2X
transmission UE without the command of the base station, when an
RSRP value measured by the V2X reception UE with the base station
is equal to or greater than (or greater than) a specific threshold
value configured by the base station or is equal to or less than
(or less than) a specific threshold value, the V2X reception UE may
transmit the request of the signal for path loss estimation to the
V2X transmission UE. In this case, the base station may configure
the RSRP threshold value in the V2X reception UE through a system
transmission block for V2X (V2X SIB) or a UE-specific RRC/common
RRC message for V2X. In another example, when a variation of the
RSRP value with the base station is equal to or greater than (or
greater than) a specific threshold value configured by the base
station, the V2X reception UE may transmit the request for
transmission of the signal for path loss estimation to the V2X
transmission UE. Although the V2X reception UE satisfies a
condition for the RSRP value configured by the base station, when
the base station sends a command for stopping transmitting the
request for transmission of the signal for path loss estimation,
the V2X reception UE may stop transmitting the request for
transmission of the signal for path loss estimation.
[0309] In another example where the V2X reception UE transmits the
request of the signal for path loss estimation to the V2X
transmission UE without the command of the base station, when an
RSRP value of a sidelink channel measured by the V2X reception UE
is equal to or greater than (or greater than) a specific threshold
value configured by the base station or is equal to or less than
(or less than) a specific threshold value, the V2X reception UE may
transmit the request for transmission of the signal for path loss
estimation to the V2X transmission UE. In this case, the base
station may configure the RSRP value of the sidelink channel in the
V2X reception UE through a system transmission block for V2X (V2X
SIB) or a UE-specific RRC/common RRC message for V2X. In this case,
when the RSRP value of the sidelink channel satisfies a specific
threshold value condition configured by the base station at least
once, the V2X reception UE may transmit the request for
transmission of the signal for path loss estimation to the V2X
transmission UE. Alternatively, when the RSRP value of the sidelink
channel satisfies the specific threshold value condition configured
by the base station X times (or more), the V2X reception UE may
transmit the request of the signal for path loss estimation to the
V2X transmission UE. In this case, X may be pre-defined, or may be
configured by the base station. In another example, when a
variation of the RSRP value of the sidelink channel is equal to or
greater than (or greater than) a specific threshold value
configured by the base station, the V2X reception UE may transmit
the request for transmission of the signal for path loss estimation
to the V2X transmission UE. Even when the V2X reception UE
satisfies a condition for the RSRP value of the sidelink channel,
which is configured by the base station, when the base station
transmits a command for stopping transmitting the request for
transmission of the signal for path loss estimation, the V2X
reception UE may stop transmitting the request for transmission of
the signal for path loss estimation. In another example, a
threshold value for the RSRP value of the sidelink channel or the
variation of the RSRP value of the sidelink channel may be
pre-configured without signaling from the base station.
[0310] In the above examples in which the V2X reception UE
transmits the request for transmission of the signal for path loss
estimation, V2X transmission UEs may refer to UEs having a
capability to transmit a signal for V2X path loss estimation.
Accordingly, it may be assumed that the V2X reception UE may
previously know information on the V2X transmission UEs having the
capability to transmit the signal for path loss estimation.
[0311] As shown in FIG. 9, the base station may transmit a command
for transmission of the request of the signal for path loss
estimation to the V2X reception UE, and whether the V2X
transmission UE is capable of transmitting the signal for path loss
estimation may be a V2X UE capability (i.e., only UEs having a
capability to transmit a signal for V2X path loss estimation may
transmit the signal for V2X path loss estimation). Accordingly, the
base station may transmit the command to the V2X reception UE by
considering the capability of the V2X transmission UE. In this
case, the command of the base station may be transmitted to the V2X
reception UE through UE-specific DCI (or group common DCI) for a
sidelink or through UE-specific RRC. The V2X reception UE receiving
the command for transmission of the request of the signal for path
loss estimation may transmit the request for transmission of the
signal for path loss estimation to the V2X transmission UE.
Alternatively, when the above condition is satisfied (i.e.,
expiration of a timer, RSRP with the base station, or a modulation
order), the V2X reception UE that is to transmit the request for
transmission of the signal for path loss estimation may transmit
the request for transmission of the signal for path loss estimation
to the V2X transmission UE. The V2X transmission UE receiving the
request may transmit the signal for path loss estimation to the V2X
reception UE. In this case, the V2X reception UE may obtain
information on transmission power of the signal for path loss
estimation from the V2X transmission UE by using various
methods.
[0312] A method of transmitting the information on the transmission
power of the signal for path loss estimation may be performed in
various ways as described with reference to FIG. 8A. Also, a method
of configuring transmission power information of the signal for
path loss estimation may be performed by using one of various
examples described with reference to FIG. 8A. The V2X reception UE
receiving the signal for path loss estimation and the transmission
power information of the signal for path loss estimation from the
base station or the V2X transmission UE may estimate a path loss
value of a sidelink by using [Equation 1], and may report the
estimated path loss value to the V2X transmission UE. In another
example, as described with reference to FIG. 8A, the V2X reception
UE may report an RSRP value measured by the V2X reception UE
itself, instead of reporting a path loss value. For a reporting
method, a channel in which reported information is transmitted, a
resource in which reported information is transmitted, a point of
time when reported information is transmitted, and a method of
configuring an initial transmission power value of a channel in
which reported information is transmitted, there may be various
methods as described with reference to FIG. 8A.
[0313] Until an estimated sidelink path loss value in FIGS. 8A and
9 is reflected in transmission of actual sidelink control
information and data information, there are pieces of information
to be transmitted and received between the V2X transmission UE and
the V2X reception UE. To transmit the pieces of information, it may
be necessary to consider how to configure a transmission power
value. For example, in FIG. 8A, the V2X reception UE may estimate a
sidelink path loss value by using a signal for path loss estimation
received from the V2X transmission UE, and may configure a
transmission power value of sidelink control information and data
information based on the estimated sidelink path loss value. In
this case, it may be necessary to determine how to configure a
transmission power value of the signal for path loss estimation
transmitted to the V2X reception UE. Also, in FIG. 9, the V2X
reception UE may transmit a request for transmission of the signal
for path loss estimation to the V2X transmission UE, and the V2X
transmission UE may transmit a signal for sidelink path loss
estimation to the V2X reception UE based on the request. In this
case, it may be necessary to determine how to configure
transmission power values of the request for transmission of the
signal for path loss estimation transmitted by the V2X reception UE
to the V2X transmission UE and the signal for sidelink path loss
estimation transmitted by the V2X transmission UE to the V2X
reception UE. In this case, at least one of the following methods
may be used.
[0314] Pre-Defined Transmission Power Value is Used [0315] A base
station may configure a transmission power value through a V2X
dedicated SIB or RRC signaling. In this case, the configured
transmission power value may be a maximum transmission power value
of a UE (e.g., Pcmax), or an arbitrary value less than the maximum
transmission power value of the UE. In this case, the base station
may perform configuration by considering coverage of a sidelink and
interference of sidelink communication with an uplink of the base
station. The transmission power value may be used for all
transmissions until a sidelink path loss value is reflected in
transmission power value configuration of actual sidelink control
information and data information. [0316] In another example, a
transmission power value may be pre-configured without signaling
from the base station. The transmission power value may be used for
all transmissions until a sidelink path loss value is reflected in
transmission power value configuration of actual sidelink control
information and data information.
[0317] Transmission Power Value Reflecting a Sidelink Path Loss
Value Estimated by Itself is Used [0318] In FIG. 9, the V2X
transmission UE may receive a request for transmission of a signal
for path loss estimation from the V2X reception UE. When this
procedure is used, the V2X transmission UE may measure sidelink
RSRP and may measure a path loss value by using the request signal
transmitted from the V2X reception UE. In this case, a transmission
power value of the request of the signal for path loss estimation,
transmitted from the V2X reception UE, may be obtained by the V2X
reception UE by using embodiments using the pre-defined
transmission power value. The V2X transmission UE may configure a
transmission power value of the signal for path loss estimation
transmitted to the V2X reception UE based on the path loss value
estimated by the V2X transmission UE itself.
[0319] Transmission Power Value Reflecting a Downlink Path Loss
Value with a Base Station Estimated by Itself is Used [0320] When a
V2X transmission UE exists in coverage of a base station, the V2X
transmission UE may measure downlink RSRP and estimate a downlink
path loss value by using an SSB or a CSI-RS of the base station.
The V2X transmission UE may configure a transmission power value of
a signal for sidelink path loss estimation transmitted to the V2X
reception UE based on the downlink path loss value. [0321] When the
V2X reception UE exists in coverage of the base station, the V2X
reception UE may estimate a downlink path loss value with the base
station (or RSU) by using an SSB or a CSI-RS of the base station.
The V2X reception UE may configure a transmission power value of
transmission request information of a signal for sidelink path loss
estimation transmitted to the V2X transmission UE, based on the
downlink path loss value with the base station. [0322] When both
the V2X reception UE and the V2X transmission UE exist in coverage
of the base station, the V2X transmission UE may measure downlink
RSRP and may estimate a path loss value by using an SSB or a CSI-RS
of the base station. Also, the V2X reception UE may estimate a
downlink path loss value with the base station (or RSU) by using
the SSB or the CSI-RS of the base station. In this case, in FIG. 9,
the V2X reception UE may configure a transmission power value of
transmission request information transmission of a signal for
sidelink path loss estimation transmitted to the V2X transmission
UE based on the downlink path loss value estimated by the V2X
reception UE itself. The V2X transmission UE may configure a
transmission power value of the signal for sidelink path loss
estimation transmitted to the V2X reception UE based on the
downlink path loss value with the base station.
[0323] FIG. 10 is a diagram illustrating a method of transmitting
and receiving a path loss measurement signal to estimate an
inter-UE sidelink path loss, according to another embodiment of the
present disclosure.
[0324] In detail, FIG. 10 is a diagram illustrating a method of
estimating a path loss in both directions. In this case, estimation
in both directions may refer to a case where a V2X reception UE
estimates a path loss value by receiving a signal for path loss
estimation transmitted by a V2X transmission UE and the V2X
transmission UE estimates a path loss value by receiving a signal
for path loss estimation transmitted by the V2X reception UE.
[0325] V2X UEs in coverage of a base station may perform downlink
synchronization and may obtain system information. In this case,
the downlink synchronization may be performed through a primary
synchronization signal/secondary synchronization signal (PSS/SSS)
received from the base station, or may be performed through a
synchronization signal received from a global navigation satellite
system (GNSS). The V2X UEs performing the downlink synchronization
may obtain system information related to V2X through a V2X
dedicated system information block (SIB) transmitted by the base
station gNB/RSU. Also, the V2X UEs in the coverage may perform
uplink synchronization through a random access procedure with a
base station and may perform an RRC connection procedure. In this
case, the uplink synchronization and the RRC connection procedure
may be performed by only one of a transmission UE or a reception
UE, or may be performed by both the transmission UE and the
reception UE.
[0326] Information on which UE from among the transmission UE and
the reception UE is to perform the uplink synchronization and the
RRC connection procedure may vary according to a transmission mode
of sidelink control information/data information, a sidelink path
loss estimation procedure, a signaling method, etc. For example, as
shown in FIG. 8A, a mode in which the base station transmits a
command for transmission of a path loss signal to a V2X
transmission UE, the transmission UE may have to perform the uplink
synchronization and the RRC connection procedure with the base
station. Also, as shown in FIG. 9, in a mode in which the base
station transmits a command for transmission of a path loss signal
to a V2X reception UE, the reception UE may have to perform the
uplink synchronization and the RRC connection procedure with the
base station.
[0327] As shown in FIG. 10, when the base station transmits a
command for transmission of a signal for path loss estimation to
both the V2X reception UE and the V2X transmission UE, both the
reception UE and the transmission UE may perform the uplink
synchronization and the RRC connection procedure with the base
station according to a signaling method by which the base station
transmits a command for transmission of a path loss signal For
example, when the command for transmission of the path loss signal
is transmitted through UE-specific DCI (or group-common DCI) or
UE-specific RRC signaling, the reception UE and the transmission UE
may perform the uplink synchronization and the RRC connection
procedure with the base station. When the command for transmission
of the path loss signal is transmitted through a V2X dedicated SIB,
the reception UE and the transmission UE may not perform the uplink
synchronization and the RRC connection procedure with the base
station.
[0328] In FIG. 10, a reception UE may refer to a UE that receives
sidelink control information and data information, and a
transmission UE may refer to a UE that transmits sidelink control
information and data information. Accordingly, the reception UE and
the transmission UE in FIG. 10 may not be related to transmission
and reception of a path loss signal.
[0329] A V2X transmission UE or a V2X reception UE may perform
unicast link configuration. The unicast link configuration may be
performed in a higher layer (e.g., an application layer), and as
shown in FIG. 10, the unicast link configuration may be performed
between the V2X transmission UE that is to transmit V2X control
information/data information in a unicast method and the V2X
reception UE that is to receive the V2X control information/data
information in the unicast method. Also, although not shown in FIG.
10, the base station may engage in the unicast link configuration.
For example, the V2X transmission UE may transmit a request for the
unicast link configuration to the base station, and the base
station may transmit a response to the unicast link configuration
to the V2X reception UE. Also, the base station may transmit a
confirmation for the unicast link configuration to the V2X
transmission UE and the V2X reception UE. However, as described
above, because this procedure may be performed in the higher layer,
the procedure may not be identified in a physical layer and a MAC
layer.
[0330] As shown in FIG. 10, the base station may transmit a command
for transmission of a signal for path loss estimation to the V2X
transmission UE and the V2X reception UE. In this case, the command
of the base station may be transmitted to the V2X transmission UE
through UE-specific DCI (group common DCI) for a sidelink or
through a MAC CE or UE-specific RRC. When the command for
transmission of the signal for path loss estimation is transmitted
through the UE-specific DCI or the group common DCI, the DCI may
use a radio network temporary identifier (RNTI) different from
UE-specific DCI or group common DCI used in existing cellular
communication for distinguishment from existing cellular
communication. When the base station transmits the command for
transmission of the signal for path loss estimation to the V2X
transmission UE and the V2X reception UE through an SIB,
UE-specific RRC, or common RRC signaling, RRC parameters may
include at least one of a time resource, a frequency resource, and
a code resource in which the signal for path loss estimation is
transmitted. In this case, the time resource may include at least
one information from among a start point at which the signal for
path loss estimation is transmitted (at least one of a symbol
index, a slot index, or a subframe index) and a transmission
period. The frequency resource may include at least one information
from among a start point of a resource block (RB) at which the
signal for path loss estimation is transmitted, a size of the RB, a
resource pool, and a bandwidth index (when a partial bandwidth is
used). Also, the code resource may include at least one information
from among a sequence index used for the signal for path loss
estimation, a scrambling ID, and a cyclic shift.
[0331] In another example where the signal for path loss estimation
is transmitted in both directions based on the command of the base
station, information on a transmission resource of the signal for
path loss estimation may be configured in the V2X transmission UE
and the V2X reception UE through UE-specific RRC or common RRC
signaling, and a transmission time of the signal for path loss
estimation is activated through a MAC CE, UE-specific DCI, or group
common DCI.
[0332] In another example where the signal for path loss estimation
is transmitted in both directions based on the command of the base
station, as shown in FIG. 6, when the base station transmits a
command for transmission of the signal for path loss estimation to
the V2X reception UE and the V2X reception UE transmits the signal
for path loss estimation to the V2X transmission UE, the V2X
transmission UE receiving the signal may transmit the signal for
path loss estimation to the V2X reception UE in response.
Information on when the V2X reception UE is to transmit the signal
for path loss estimation may be determined by using one of various
embodiments described with reference to FIG. 6.
[0333] As shown in FIG. 7, when the base station transmits a
command for transmission of a request of the signal for path loss
estimation to the V2X transmission UE and the V2X transmission UE
transmits the request for transmission of the signal for path loss
estimation to the V2X reception UE, the V2X reception UE receiving
the request may transmit the signal for path loss estimation to the
V2X transmission UE and the V2X transmission UE may transmit the
signal for path loss estimation to the V2X reception UE in
response. Information on when the V2X transmission UE is to
transmit the request of the signal for path loss estimation to the
V2X reception UE may be determined by using one of various
embodiments described with reference to FIG. 7.
[0334] Also, as shown in FIG. 8A, when the base station transmits a
command for transmission of the signal for path loss estimation to
the V2X transmission UE and the V2X transmission UE transmits the
signal for path loss estimation to the V2X reception UE, the V2X
reception UE receiving the signal may transmit the signal for path
loss estimation to the V2X transmission UE in response. Information
on when the V2X transmission UE is to transmit the signal for path
loss estimation may be determined by using one of various methods
described with reference to FIG. 8A.
[0335] Lastly, as shown in FIG. 9, when the base station transmits
a command for transmission of a request for transmission of the
signal for path loss estimation to the V2X reception UE and the V2X
reception UE transmits the request for transmission of the signal
for path loss estimation to the V2X transmission UE, the V2X
transmission UE receiving the request may transmit the signal for
path loss estimation to the V2X reception UE and the V2X reception
UE may transmit the signal for path loss estimation to the V2X
transmission UE in response. Information on when the V2X reception
UE is to transmit the request of the signal for path loss
estimation may be determined by using one of various embodiments
described with reference to FIG. 9.
[0336] Also, unlike in FIG. 10, the V2X transmission UE and the V2X
reception UE may transmit and receive the signal for path loss
estimation after unicast link configuration, without the command of
the base station. For example, the V2X transmission UE may start a
timer from a point of time when a request for unicast link
configuration is received or from a point of time when the unicast
link configuration succeeds, and may transmit the signal for path
loss estimation at a point of time when the timer expires.
Likewise, the V2X reception UE may start a timer from a point of
time when a request for unicast link configuration is transmitted
or from a point of time when the unicast link configuration
succeeds, and may transmit the signal for path loss estimation to
the V2X transmission UE at a point of time when the timer expires.
In another example, the V2X transmission UE may transmit the signal
for path loss estimation after a certain period of time (e.g.,
after [x] subframes, [x] slots, or [x] ms) from a point of time
when unicast link configuration succeeds. Likewise, the V2X
reception UE may transmit the signal for path loss estimation to
the V2X transmission UE after a certain period of time (e.g., [x]
subframes, [x] slots, or [x] ms) from a point of time when unicast
link configuration succeeds.
[0337] In another example where the V2X transmission UE and the V2X
reception UE transmit the signal for path loss estimation without
the command of the base station, pre-defined (pre-configured)
parameters may be used and may include at least one of a time
resource, a frequency resource, and a code resource in which the
signal for path loss estimation is transmitted. In this case, the
time resource may include at least one information from among a
start point at which the signal for path loss estimation is
transmitted (at least one of a symbol index, a slot index, or a
subframe index) and a transmission period. The frequency resource
may include at least one information from among a start point of a
resource block (RB) at which the signal for path loss estimation is
transmitted, a size of the RB, a resource pool, and a bandwidth
index (when a partial bandwidth is used). Also, the code resource
may include at least one information from among a sequence index
used for the signal for path loss estimation, a scrambling ID, and
a cyclic shift.
[0338] In another example where the V2X transmission UE and the V2X
reception UE transmit the signal for path loss estimation without
the command of the base station, as shown in FIG. 6, when the V2X
reception UE transmits the signal for path loss estimation to the
V2X transmission UE, the V2X transmission UE receiving the signal
may transmit the signal for path loss estimation to the V2X
reception UE in response. Information on when the V2X reception UE
is to transmit the signal for path loss estimation may be
determined by using one of various embodiments described with
reference to FIG. 6.
[0339] Also, as shown in FIG. 7, when the V2X transmission UE
transmits a request for transmission of the signal for path loss
estimation to the V2X reception UE, the V2X reception UE receiving
the request may transmit the signal for path loss estimation to the
V2X transmission UE and the V2X transmission UE may transmit the
signal for path loss estimation to the V2X reception UE in
response. Information on when the V2X transmission UE is to
transmit the request of the signal for path loss estimation to the
V2X reception UE may be determined by using one of various
embodiments described with reference to FIG. 7.
[0340] Also, as shown in FIG. 8A, when the V2X transmission UE
transmits the signal for path loss estimation to the V2X reception
UE, the V2X reception UE receiving the signal may transmit the
signal for path loss estimation to the V2X transmission UE in
response. Information on when the V2X transmission UE is to
transmit the signal for path loss estimation may be determined by
using one of various embodiments described with reference to FIG.
8A.
[0341] Lastly, as shown in FIG. 9, when the V2X reception UE
transmits the request for transmission of the signal for path loss
estimation to the V2X transmission UE, the V2X transmission UE
receiving the request may transmit the signal for path loss
estimation to the V2X reception UE and the V2X reception UE may
transmit the signal for path loss estimation to the V2X
transmission UE in response. Information on when the V2X reception
UE is to transmit the request of the signal for path loss
estimation to the V2X transmission UE may be determined by using of
various embodiments described with reference to FIG. 9.
[0342] Although transmission of the signal for path loss estimation
starts from the V2X transmission UE and the V2X reception UE
transmits the signal for path loss estimation to the V2X
transmission UE in response in FIG. 10, the reverse case may be
possible. That is, transmission of the signal for path loss
estimation may start from the V2X reception UE and the V2X
transmission UE may transmit the signal for path loss estimation to
the V2X reception UE in response. Information on which UE will
first transmit the signal for path loss estimation may be
pre-agreed (e.g., a transmission UE always first transmits), or may
be determined by the command of the base station.
[0343] When transmission of the signal for path loss estimation
starts from the V2X transmission UE, the V2X reception UE may
include timing information on timing at which the V2X reception UE
has to transmit the signal for path loss estimation in a sidelink
broadcast channel or a sidelink control channel. That is, the V2X
transmission UE may transmit timing-related information in a bit
field of the sidelink broadcast channel or control channel by using
[z] bits. In this case, a unit representing the [z] bits may be the
number of symbols (z1 symbols), the number of slots (z2 slots), or
the number of subframes (z3 subframes). Accordingly, the V2X
reception UE receiving the information may transmit the signal for
path loss estimation after z1 symbols (or z2 slots or z3 subframes)
from a point of time when the bit field is received. In another
example, the timing information may be fixed, and the V2X
transmission UE and the V2X reception UE may use a pre-agreed
value. In another example, when the V2X transmission UE and the V2X
reception UE are located in the same base station, the base station
may configure the timing information. In another example, the V2X
transmission UE may transmit the timing information configured by
the base station via the sidelink broadcast channel or the sidelink
control channel, to a V2X reception UE existing out of coverage of
the base station or a V2X reception UE existing in a different base
station.
[0344] Even when transmission of the signal for path loss
estimation starts from the V2X reception UE, a similar operation
may be performed. That is, the V2X reception UE may operate like
the V2X transmission UE in the above example, and the V2X
transmission UE may operate like the V2X reception UE in the above
example.
[0345] A V2X UE (the V2X transmission UE or the V2X reception UE)
that transmits the signal for path loss estimation may transmit
information on transmission power of the signal for path loss
estimation. Transmission power information may be transmitted
through various embodiments described with reference to FIGS. 6
through 9.
[0346] A V2X UE (the V2X transmission UE or the V2X reception UE)
that receives the signal for path loss estimation may measure RSRP
through the received signal for path loss estimation, and may
estimate a path loss value through information on transmission
power of the obtained signal for path loss estimation. The V2X
transmission UE may configure a transmission power value for
sidelink control information and data information transmission
based on the path loss value estimated by the V2X transmission UE
itself and may perform sidelink transmission. The V2X reception UE
receiving the information may configure a transmission power value
for sidelink feedback channel transmission based on the path loss
value estimated by the V2X reception UE itself and may transmit a
sidelink feedback to the V2X transmission UE. Although a type of
information transmitted via a sidelink feedback channel is HARQ-ACK
in FIG. 10, the present disclosure is not limited thereto. For
example, the sidelink feedback information may include hybrid
ARQ-acknowledgement (HARQ-ACK), channel state information (CSI), a
rank indicator (RI), a precoder matrix indicator (PMI), a layer
indicator (LI), or a scheduling request (SR) of a sidelink channel.
Also, the various feedback information may be multiplexed and may
be transmitted via the sidelink feedback channel.
[0347] FIG. 11 is a flowchart illustrating a path loss estimation
operation of a transmission UE, according to a disclosed
embodiment.
[0348] FIG. 11 illustrates an operation of a transmission UE of
FIGS. 5, 8A, and 9.
[0349] First, in operation 1110, a transmission UE transmits a
signal for path loss estimation to a reception UE. In an
embodiment, examples of the signal for path loss estimation may
include a sidelink synchronization signal such as a primary
sidelink synchronization signal (PSSS) or a secondary sidelink
synchronization signal (SSSS), a demodulation reference signal
(DMRS) transmitted via a sidelink broadcast channel (physical
sidelink broadcast channel (PSBCH)), a sidelink control channel
(physical sidelink control channel (PSCCH)), or a sidelink data
channel (physical sidelink shared channel (PSSCH)), and a reference
signal for supporting a sidelink operation such as a sidelink
sounding reference signal (SRS), a sidelink channel state
information reference signal (CSI-RS), or a sidelink phase tracking
reference signal (PTRS).
[0350] Also, the transmission UE may transmit the signal for path
loss estimation to the reception UE, at a point of when the
transmission UE receives a command for transmission of the signal
for path loss estimation from a base station, when reference signal
received power (RSRP) measured by the transmission UE for a signal
for downlink path loss estimation transmitted by the base station
is equal to or greater than a configured threshold value or equal
to or less than a configured threshold value, when the transmission
UE determines that the signal for path loss estimation needs to be
transmitted, or when the transmission UE receives a transmission
request signal of the signal for path loss estimation from the
reception UE.
[0351] Also, in an embodiment, the transmission UE may configure,
as transmission power of the signal for path loss estimation,
pre-configured transmission power, maximum transmission power of
the transmission UE, transmission power according to configuration
of the base station, transmission power determined based on RSRP
measured by the transmission UE for a signal for downlink path loss
estimation transmitted by the base station, or transmission power
determined based on RSRP measured by the transmission UE for a
transmission request signal of the signal for path loss estimation
received from the reception UE.
[0352] Next, in operation 1120, the transmission UE receives a path
loss estimation result report from the reception UE in response to
the signal for path loss estimation. In an embodiment, the path
loss estimation result report may include layer 1 RSRP (L1-RSRP)
measured by the reception UE, layer 3 RSRP (L3-RSRP), and a path
loss value estimated by the reception UE. Also, the transmission UE
may receive the path loss estimation result report via a sidelink
feedback channel, a sidelink control channel, a sidelink data
channel, or a MAC control element (CE). Furthermore, when the
transmission UE receives the path loss estimation result report via
the above channels, the transmission UE may allocate and control a
resource in which reported information is transmitted in order to
prevent collision and interference between resources of different
V2X UEs.
[0353] Also, in an embodiment, the transmission UE may periodically
or aperiodically receive the path loss estimation result report
according to configuration of the base station and sidelink control
information.
[0354] In operation 1130, the transmission UE configures
transmission power based on the path loss estimation result
report.
[0355] Next, in operation 1140, the transmission UE may perform
sidelink transmission with the reception UE with the configured
transmission power. In an embodiment, the transmission UE may
transmit sidelink control information and sidelink data with the
configured transmission power.
[0356] Furthermore, in an embodiment, the transmission UE may
transmit information on the transmission power of the signal for
path loss estimation to the reception UE. In an embodiment, the
transmission UE may transmit a transmission power value of the
signal for path loss estimation, and offset information between a
configured reference signal and the transmission power value of the
signal for path loss estimation to the reception UE. In this case,
the signal for path loss estimation and the information on the
transmission power of the signal for path loss estimation may be
transmitted via the same channel or different channels.
[0357] FIG. 12 is a flowchart illustrating a path loss estimation
operation of a reception UE, according to a disclosed
embodiment.
[0358] FIG. 12 illustrates an operation of a reception UE of FIGS.
5, 8A, and 9.
[0359] First, in operation 1210, a reception UE receives a signal
for path loss estimation from a transmission UE. In an embodiment,
examples of the signal for path loss estimation may include a
sidelink synchronization signal such as a primary sidelink
synchronization signal (PSSS) or a secondary sidelink
synchronization signal (SSSS), a demodulation reference signal
(DMRS) transmitted via a sidelink broadcast channel (physical
sidelink broadcast channel (PSBCH)), a sidelink control channel
(physical sidelink control channel (PSCCH)), or a sidelink data
channel (physical sidelink shared channel (PSSCH)), and a reference
signal for supporting a sidelink operation such as a sidelink
sounding reference signal (SRS), a sidelink channel state
information reference signal (CSI-RS), or a sidelink phase tracking
reference signal (PTRS).
[0360] Next, in operation 1220, the reception UE estimates a path
loss based on the signal for path loss estimation.
[0361] In operation 1230, the reception UE transmits a path loss
estimation result report to the transmission UE. In an embodiment,
the path loss estimation result report may include layer 1 RSRP
(L1-RSRP) measured by the reception UE, layer 3 RSRP (L3-RSRP), and
a path loss value estimated by the reception UE. Also, the
reception UE may transmit the path loss estimation result report
via a sidelink feedback channel, a sidelink control channel, a
sidelink data channel, or a MAC control element (CE). Furthermore,
when the reception UE receives the path loss estimation result
report via the above channels, the reception UE may allocate and
control a resource in which reported information is transmitted in
order to prevent collision and interference between resources of
different V2X UEs.
[0362] Also, in an embodiment the reception UE may periodically or
aperiodically transmit the path loss estimation result report
according to configuration of a base station and sidelink control
information.
[0363] In an embodiment, the reception UE may configure, as
transmission power of a path loss estimation report signal,
pre-configured transmission power, maximum transmission power of
the reception UE, transmission power according to configuration of
the base station, or transmission power determined based on RSRP
measured by the reception UE for a signal for downlink path loss
estimation transmitted by the base station.
[0364] In an embodiment, the reception UE may transmit a
transmission request signal of the signal for path loss estimation
to the transmission UE, at a point of time when the reception UE
receives a command for a transmission request of the signal for
path loss estimation from the base station, when RSRP measured by
the reception UE for a signal for downlink path loss estimation
transmitted by the base station is equal to or greater than a
configured threshold value or equal to or less than a configured
threshold value, or when the reception UE determines that the
signal for path loss estimation needs to be transmitted. In this
case, the reception UE may configure, as transmission power of the
transmission request signal of the signal for path loss estimation,
pre-configured transmission power, maximum transmission power of
the reception UE, transmission power according to configuration of
the base station, or transmission power determined based on RSRP
measured by the reception UE for a signal for downlink path loss
estimation transmitted by the base station.
[0365] Also, in an embodiment, the reception UE may receive
information on the transmission power of the signal for path loss
estimation. In an embodiment, the reception UE may receive a
transmission power value of the signal for path loss estimation,
and offset information between a configured reference signal and
the transmission power value of the signal for path loss
estimation. In this case, the signal for path loss estimation and
the information on the transmission power of the signal for path
loss estimation may be received via the same channel or different
channels.
[0366] FIG. 13 is a flowchart illustrating a path loss estimation
operation of a transmission UE, according to another disclosed
embodiment.
[0367] FIG. 13 illustrates an operation of a transmission UE of
FIGS. 4, 6, and 7.
[0368] First, in operation 1310, a transmission UE receives a
signal for path loss estimation from a reception UE. In an
embodiment, examples of the signal for path loss estimation may
include a sidelink synchronization signal such as a primary
sidelink synchronization signal (PSSS) or a secondary sidelink
synchronization signal (SSSS), a demodulation reference signal
(DMRS) transmitted via a sidelink broadcast channel (physical
sidelink broadcast channel (PSBCH)), a sidelink control channel
(physical sidelink control channel (PSCCH)), or a sidelink data
channel (physical sidelink shared channel (PSSCH)), and a reference
signal for supporting a sidelink operation such as a sidelink
sounding reference signal (SRS), a sidelink channel state
information reference signal (CSI-RS), or a sidelink phase tracking
reference signal (PTRS).
[0369] Next, in operation 1320, the transmission UE estimates a
path loss based on the signal for path loss estimation.
[0370] In operation 1330, the transmission UE configures
transmission power based on a path loss estimation result.
[0371] Next, in operation 1340, the transmission UE performs
sidelink transmission with the reception UE with the configured
transmission power. In an embodiment, the transmission UE may
transmit sidelink control information and sidelink data with the
configured transmission power.
[0372] In an embodiment, the transmission UE may transmits a
transmission request signal of the signal for path loss estimation
to the transmission UE, at a point of time when the transmission UE
receives a command for a transmission request of the signal for
path loss estimation from a base station, when RSRP measured by the
transmission UE for a signal for downlink path loss estimation
transmitted by the base station is equal to or greater than a
configured threshold value or equal to or less than a configured
threshold value, or when the transmission UE determines that the
signal for path loss estimation needs to be transmitted. In this
case, the transmission UE may configure, as transmission power of
the transmission request signal of the signal for path loss
estimation, pre-configured transmission power, maximum transmission
power of the transmission UE, transmission power according to
configuration of the base station, or transmission power determined
based on RSRP measured by the transmission UE for a signal for
downlink path loss estimation transmitted by the base station.
[0373] Also, in an embodiment, the transmission UE may receive
information on the transmission power of the signal for path loss
estimation. In an embodiment, the transmission UE may receive a
transmission power value of the signal for path loss estimation,
and offset information between a configured reference signal and
the transmission power value of the signal for path loss
estimation. In this case, the signal for path loss estimation and
the information on the transmission power of the signal for path
loss estimation may be received via the same channel or different
channels.
[0374] FIG. 14 is a flowchart illustrating a path loss estimation
operation of a reception UE, according to another disclosed
embodiment.
[0375] FIG. 14 illustrates an operation of a transmission UE of
FIGS. 4, 6, and 7.
[0376] First, in operation 1410, a reception UE transmits a signal
for path loss estimation to a transmission UE. In an embodiment,
examples of the signal for path loss estimation may include a
sidelink synchronization signal such as a primary sidelink
synchronization signal (PSSS) or a secondary sidelink
synchronization signal (SSSS), a demodulation reference signal
(DMRS) transmitted via a sidelink broadcast channel (physical
sidelink broadcast channel (PSBCH)), a sidelink control channel
(physical sidelink control channel (PSCCH)), or a sidelink data
channel (physical sidelink shared channel (PSSCH)), and a reference
signal for supporting a sidelink operation such as a sidelink
sounding reference signal (SRS), a sidelink channel state
information reference signal (CSI-RS), or a sidelink phase tracking
reference signal (PTRS).
[0377] Next, in operation 1420, the reception UE performs sidelink
transmission with the transmission UE.
[0378] In an embodiment, the reception UE may transmit a
transmission request signal of the signal for path loss estimation
to the transmission UE, at a point of time when the reception UE
receives a command for transmission of the signal for path loss
estimation from a base station, when RSRP measured by the reception
UE for a signal for downlink path loss estimation transmitted by
the base station is equal to or greater than a configured threshold
value or equal to or less than a configured threshold value, when
the reception UE determines that the signal for path loss
estimation needs to be transmitted, or when the reception UE
receives the transmission request signal of the signal for path
loss estimation from the transmission UE. In this case, the
reception UE may configure, as transmission power of the signal for
path loss estimation, pre-configured transmission power, maximum
transmission power of the reception UE, transmission power
according to configuration of the base station, transmission power
determined based on RSRP measured by the reception UE for a signal
for downlink path loss estimation transmitted by the base station,
or transmission power determined based on RSRP measured by the
reception UE for a transmission request signal of the signal for
path loss estimation received from the transmission UE.
[0379] Also, in an embodiment, the reception UE may transmit
information on the transmission power of the signal for path loss
estimation. In an embodiment, the reception UE may transmit a
transmission power value of the signal for path loss estimation,
and offset information between a configured reference signal and
the transmission power value of the signal for path loss
estimation. In this case, the signal for path loss estimation and
the information on the transmission power of the signal for path
loss estimation may be transmitted via the same channel or
different channels.
[0380] Next, in operation 1420, the reception UE performs sidelink
transmission with the transmission UE. In an embodiment, the
reception UE may receive sidelink control information and sidelink
data from the transmission UE.
[0381] Although not shown, operations of the transmission UE and
the reception UE of FIG. 10 may be similar to operations of the
transmission UE and the reception UE described with reference to
FIGS. 11 through 14. In an embodiment, some operations of the
transmission UE and the reception UE described with reference to
FIGS. 11 through 14 may be applied to operations in FIG. 10 such as
transmission and reception of a signal for path loss estimation of
the transmission UE and the reception UE, estimation of a path loss
based on the signal for path loss estimation, transmission and
reception of a path loss estimation result report corresponding to
the signal for path loss estimation, configuration of transmission
power based on the path loss estimation result report, and sidelink
transmission with the configured transmission power.
[0382] Also, although the description has been made assuming that
there are one transmission UE and one reception UE, the present
disclosure is not limited thereto and may be applied even when
there are one or more transmission UEs and reception UEs. For
example, when there are a plurality of transmission UEs and/or a
plurality of reception UEs, each of the transmission UEs and/or the
reception UEs may transmit and receive a signal for path loss
estimation.
[0383] FIG. 15 is a block diagram illustrating a structure of a
transmission UE, according to an embodiment.
[0384] As shown in FIG. 15, a transmission UE of the present
disclosure may include a transceiver 1510, a memory 1520, and a
processor 1530. The processor 1530, the transceiver 1510, and the
memory 1520 may operate according to the above-described
communication method of the transmission UE. However, elements of
the transmission UE are not limited thereto. For example, the
transmission UE may include more or fewer elements than those
illustrated in FIG. 15. In addition, the processor 1530, the
transceiver 1510, and the memory 1520 may be implemented as one
chip. Also, the processor 1530 may include at least one
processor.
[0385] The transceiver 1510 may collectively refer to a receiver
and a transmitter of the transmission UE, and may transmit and
receive a signal to and from a base station. The signal transmitted
and received to and from the base station may include control
information and data. To this end, the transceiver 1510 may include
a radio frequency (RF) transmitter that up-converts and amplifies a
frequency of a transmitted signal, and an RF receiver that performs
low-noise amplification on a received signal and down-converts a
frequency. However, this is merely an example, and elements of the
transceiver 1510 are not limited to the RF transmitter and the RF
receiver.
[0386] Also, the transceiver 1510 may receive a signal via a
wireless channel and may output a signal to the processor 1530, and
may transmit a signal output from the processor 1530 via the
wireless channel.
[0387] The memory 1520 may store a program and data required to
operate the transmission UE. Also, the memory 1520 may store
control information or data included in a signal obtained by the
transmission UE. The memory 1520 may include a storage medium such
as a read-only memory (ROM), a random-access memory (RAM), a hard
disk, a compact disc (CD)-ROM, or a digital versatile disc (DVD),
or a combination thereof.
[0388] The processor 1530 may control a series of processes so that
the transmission UE operates according to the above-described
embodiment of the disclosure. For example, the transceiver 1510 may
receive a data signal including a control signal, and the processor
1530 may determine a reception result for the data signal.
[0389] In an embodiment, the processor 1530 may transmit a signal
for path loss estimation to a reception UE, may receive a path loss
estimation result report from the reception UE in response to the
signal for path loss estimation, may configure transmission power
based on the path loss estimation result report, and may perform
sidelink transmission with the reception UE with the configured
transmission power.
[0390] Also, in an embodiment, the processor 1530 may receive a
signal for path loss estimation from a reception UE, may estimate a
path loss based on the signal for path loss estimation, may
configure transmission power based on a path loss estimation
result, and may perform sidelink transmission with the reception UE
with the configured transmission power.
[0391] FIG. 16 is a block diagram illustrating a structure of a
reception UE, according to an embodiment.
[0392] As shown in FIG. 16, a reception UE of the present
disclosure may include a transceiver 1610, a memory 1620, and a
processor 1630. The processor 1630, the transceiver 1610, and the
memory 1620 may operate according to the above-described
communication method of the reception UE. However, elements of the
reception UE are not limited thereto. For example, the reception UE
may include more or fewer elements than those illustrated in FIG.
16. In addition, the processor 1630, the transceiver 1610, and the
memory 1620 may be implemented as one chip. Also, the processor
1630 may include at least one processor.
[0393] The transceiver 1610 may collectively refer to a receiver
and a transmitter of the reception UE, and may transmit and receive
a signal to and from a base station. The signal transmitted and
received to and from the base station may include control
information and data. To this end, the transceiver 1610 may include
an RF transmitter that up-converts and amplifies a frequency of a
transmitted signal, and an RF receiver that performs low-noise
amplification on a received signal and down-converts a frequency.
However, this is merely an example, and elements of the transceiver
1610 are not limited to the RF transmitter and the RF receiver.
[0394] Also, the transceiver 1610 may receive a signal via a
wireless channel and may output a signal to the processor 1630, and
may transmit a signal output from the processor 1630 via the
wireless channel.
[0395] The memory 1620 may store a program and data required to
operate the reception UE. Also, the memory 1620 may store control
information or data included in a signal obtained by the reception
UE. The memory 1620 may include a storage medium such as a ROM, a
RAM, a hard disk, a CD-ROM, or a DVD, or a combination thereof.
[0396] The processor 1630 may control a series of processes so that
the reception UE operates according to the above-described
embodiment of the disclosure. For example, the transceiver 1610 may
receive a data signal including a control signal, and the processor
1630 may determine a reception result for the data signal.
[0397] In an embodiment, the processor 1630 may control to receive
a signal for path loss estimation from a transmission UE, estimate
a path loss based on the signal for path loss estimation, and
transmit a path loss estimation result report to the transmission
UE.
[0398] Also, in an embodiment, the processor 1630 may transmit a
signal for path loss estimation to a transmission UE, and may
perform sidelink transmission with the transmission UE.
[0399] The methods according to the claims or embodiments of the
present disclosure described herein may be implemented by hardware,
software, or a combination of hardware and software.
[0400] When the methods are implemented by software, a
computer-readable storage medium or a computer program product
storing one or more programs (software modules) may be provided.
The one or more programs stored in the computer-readable storage
medium or the computer program product are configured to be
executable by one or more processors in an electronic device. The
one or more programs include instructions for allowing the
electronic device to execute the methods according to the claims or
embodiments of the present disclosure described herein.
[0401] These programs (software modules or software) may be stored
in a random-access memory (RAM), a non-volatile memory including a
flash memory, a read-only memory (ROM), an electrically erasable
programmable read-only memory (EEPROM), a magnetic disc storage
device, a compact disc (CD)-ROM, a digital versatile disc (DVD),
another optical storage device, or a magnetic cassette.
Alternatively, the programs may be stored in a memory configured by
combining some or all of the storage devices. Also, each of the
memories may include a plurality of memories.
[0402] Also, the programs may be stored in an attachable storage
device that is accessible through a communication network, such as
the Internet, an intranet, a local area network (LAN), a wide LAN
(WLAN), or a storage area network (SAN), or a combination thereof.
Such a storage device may access a device performing an embodiment
of the present disclosure through an external port. Also, a
separate storage device in a communication network may access a
device performing an embodiment of the present disclosure.
[0403] In detailed embodiments of the present disclosure,
components included in the present disclosure have been expressed
as singular or plural according to the detailed embodiments of the
present disclosure. However, singular or plural expressions have
been selected properly for a condition provided for convenience of
description, and the present disclosure is not limited to singular
or plural components. Components expressed as plural may be
configured as a single component, or a component expressed as
singular may be configured as plural components.
[0404] The embodiments of the disclosure disclosed in the present
specification and drawings have been provided to easily describe
the present disclosure and to help with the understanding of the
disclosure, and are not intended to limit the scope of the present
disclosure. That is, it is obvious to one of ordinary skill in the
art that various modifications may be made based on the technical
spirit of the present disclosure. Also, the embodiments of the
present disclosure may be used in combination when necessary. For
example, parts of an embodiment and another embodiment of the
present disclosure may be combined with each other. Also, other
modifications based on the technical spirit of the embodiment may
be made in other systems such as an LTE system, a 5G or NR system,
etc.
* * * * *